JP2009144168A - Modified coal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating agent for coal which can control hygroscopicity and spontaneous ignition of coal. <P>SOLUTION: The coating agent for coal comprises soluble component contained in an extracted solution separated by a method having an extraction process for mixing a non-hydrogen-donating solvent with raw material coal of a coating agent and extracting the soluble component of the raw material coal in the non-hydrogen-donating solvent and a solid-liquid separation process for separating the extraction residue from the extracted solution after the extraction process. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coating agent for coal for suppressing the hygroscopicity and pyrophoricity of coal.

  Conventionally, when coal is stored as a stock pile or in a silo, the stored coal accumulates heat by low-temperature oxidation and rises in temperature, resulting in spontaneous ignition. Subbituminous coal and lignite with a low degree of carbonization have many functional groups containing oxygen and have a fine pore structure. Therefore, when they are in a dry state, they are much more likely to spontaneously ignite than high-carbon coals such as bituminous coal. Therefore, it is difficult to store subbituminous coal and lignite as they are for a long time. In order to store coal for a long period of time, it is important to control the temperature to prevent spontaneous ignition of the coal, and it is usually practiced to sprinkle water toward the coal to suppress the oxidative heat storage of the coal. Such sprinkling is not economical and can lead to a reduction in the calorific value of the coal that prevents efficient use of the coal.

  By the way, despite the presence of many low-grade coals such as sub-bituminous coal and lignite in the world, most of the coal currently used in Japan is bituminous coal. This is because low-grade coal is not economical to transport because of its high water content, and has the above-mentioned problem of spontaneous ignition. Further, low-grade coal has a reason that the moisture content of about 10% easily occurs because the hydrophilic oxygen functional group is exposed, resulting in a low calorific value.

  In this way, it has the problem of heat storage and moisture absorption of coal that restricts the use of low-grade coal. As a technique for solving each of these problems, a sincol process, an encore process, a miller process, a DK process, and the like have been proposed (see, for example, Patent Document 1), and the development of other techniques is also in progress.

JP 58-142990 A (the first page, lower right column)

  In view of the above circumstances, an object of the present invention is to provide a coating agent for coal that can suppress the hygroscopicity and spontaneous ignition of coal.

  The present inventor has found that when coal is coated with a predetermined coal component, natural oxidation and moisture absorption of the coal can be suppressed, and the present invention has been completed.

  That is, the present invention comprises a non-hydrogen-donating solvent and a coating agent raw coal, an extraction step for extracting soluble components of the raw coal into the solvent, an extraction residue and an extract after the extraction step, And a solid-liquid separation step of separating the coal. A coal coating agent comprising the soluble component contained in the extract separated by the method. In the present invention, the “coal coating agent” is a soluble component of raw coal extracted with a non-hydrogen-donating solvent, and a solvent containing this soluble component is also an object.

  Moreover, this invention is a modified coal which has coal and the coating layer which coat | covers the surface of this coal, Comprising: The said coating layer is a modified coal which consists of the said coating agent for coal. The extraction residue which the coal coat | covered with the said coating layer isolate | separated at the said solid-liquid separation process may be sufficient. Such modified coal can also be used as coke raw coal.

  The present invention also includes an extraction step in which a non-hydrogen-donating solvent and a coating agent raw material coal are mixed and a soluble component of the coal is extracted into the solvent, and an extraction residue and an extract after the extraction step, And a solid-liquid separation step of separating the coal.

  Moreover, this invention is a manufacturing method of the modified coal which coats the coal coating agent manufactured with the manufacturing method of the said coating agent for coal on the coal surface. The coal to be coated by this method may be an extraction residue separated in the solid-liquid separation step. The modified coal produced by this method can also be used for coke raw material coal.

  According to the coating agent of the present invention, a predetermined component realizes a surface coating that suppresses moisture absorption and spontaneous ignition of coal, and enables long-term storage of coal and suppresses a decrease in calorific value of coal. it can.

It is a graph showing the result of the oxidation reaction test of the coated coal. It is a graph showing the result of the moisture absorption test of the coated coal.

  The present invention will be described below based on embodiments. The coating agent in this embodiment is a coal coating agent having a coal component that is solvent extracted. This coating agent for coal is extracted after mixing the solvent and coating material raw coal (hereinafter sometimes referred to as “raw coal”) and extracting the soluble components of the coal into the solvent. The raw material coal component contained in the extract separated by the method which has the solid-liquid process which isolate | separates a residue and an extract is included.

A non-hydrogen donating solvent is used as the solvent in the extraction step. Common aromatic compounds such as benzene, toluene, and xylene generally used as solvents have a low extraction rate of raw coal components, and when the extraction temperature is set high, the pressure for the setting becomes high. In addition, when a polar solvent such as N-methylpyrrolidone or pyridine is used, the extraction rate of the raw coal component is high, but the solvent used is strongly bonded to the raw coal and the solvent can be removed from the raw coal. It becomes difficult. In addition, in the case of an aromatic compound having three or more rings such as anthracene, since the boiling point is too high, it is difficult to separate the raw coal from the solvent. Furthermore, hydrogen donating solvents such as tetralin used in coal liquefaction methods solubilize or liquefy raw coal and show a high extraction rate, but hydrogen in the solvent is lost by moving to raw coal molecules, Even after solvent recovery, it cannot be reused immediately. For the above reasons, in this embodiment, a non-hydrogen donating solvent is used as the extraction solvent.

  The non-hydrogen-donating solvent includes a bicyclic aromatic solvent having a boiling point of about 200 to 250 ° C. obtained by a coal carbonization process or a catalytic cracking process of heavy petroleum oil, such as methylnaphthalene, A solvent mainly composed of one or more selected from naphthalene and tar gas oil is preferably used.

  The raw coal may be either high grade coal or low grade coal, and is not limited. That is, anthracite, bituminous coal, subbituminous coal, lignite, and the like are applicable. When extracting a component from this raw material coal, it is appropriate to grind | pulverize to 5 mm or less.

  In the extraction process, in order to increase the extraction rate of the raw material coal component, the raw material coal and the solvent are mixed in a slurry state. When this slurry is heated, raw material coal components are extracted into the solvent. The extraction temperature at that time is preferably set to 300 to 420 ° C. When the temperature is lower than 300 ° C., the efficiency of removing the easily gasified component of the raw coal component from the raw coal is poor, and it is insufficient to weaken the bonding force between the raw coal constituent molecules, The extraction rate of the raw coal component into the solvent will be low. On the other hand, even when the temperature is higher than 420 ° C., the recombination of radicals generated by the thermal decomposition reaction of the raw coal occurs, so that the extraction rate of the raw coal component into the solvent is lowered. Note that the pressure is adjusted so that the solvent does not reach the boiling point even at the extraction temperature, and it is usually preferable to adjust the pressure in the range of 0.8 to 2.5 MPa. Further, extraction is performed in the presence of an inert gas (for example, nitrogen).

  The solid-liquid separation step separates the extraction residue of the raw coal that was insoluble in the solvent and the solvent containing the raw coal component that was soluble in the solvent (hereinafter, “extract”). For example, it is separated by a gravity sedimentation method or a filtration method for separating the upper solvent and the lower coal in the settling tank. In the filtration method, since the filtration amount of the filtration filter is limited, it is preferable to employ a sedimentation method in order to separate a large amount of extraction residue. In the solid-liquid separation step, it is preferable to set the solvent temperature and pressure within the same temperature and pressure range set in the extraction step.

  The extract after the solid-liquid separation can be used as a coating agent, and only the solvent-soluble component (softening start temperature: 100 to 300 ° C.) of the raw material coal obtained by removing the solvent from the extract is used for coal. It can also be used as a coating agent.

  Next, the usage method of the coating agent of this embodiment is demonstrated. Coal to be coated with the coating agent of this embodiment is not limited to the type of coal such as bituminous coal, subbituminous coal, lignite. In addition, it is allowed to be used for coating the extraction residue obtained in the solid-liquid separation step in the production of the coating agent. Coal whose surface is coated with a coating agent layer is modified. That is, the direct contact between the highly active and highly hydrophilic oxygen-containing functional group exposed on the coal surface and the outside atmosphere is prevented, so that the oxidation reaction (spontaneous ignition) is suppressed. And it becomes possible to suppress the moisture absorption of coal by reducing the hydrophilicity of the coal surface.

  The specific coating of the coal surface is, for example, (a) a mixed solution of a coating agent and a solvent having an appropriately set concentration (preferably kept at 300 to 420 ° C. where the coating agent is uniformly dispersed) After mixing the slurry with coal, the solvent is evaporated and removed by distillation or spray drying to form a coating layer on the surface of the coal. Ash charcoal) is heated to 100-350 ° C., and the coating agent that has been softened and melted and liquefied is sprayed onto the coal to form a coating agent layer on the coal surface, and (c) a solvent in which the coating agent is dissolved. There is a method of removing the solvent after dripping or spraying on the coal to wet the surface of the coal.

  The coating amount is preferably 3 to 20% by weight of coal. If the amount is less than 3% by weight, the oxidation reaction and the moisture absorption suppressing effect are small.

  The coating agent of this embodiment can also be used as a coating agent for coke raw coal. By the way, when the coating agent itself is a raw material for coke for coke, it becomes a raw material for coke with improved softening and melting characteristics, so that coal of lower quality than before can be included in the mixed coal. However, when a small amount of the coating agent is added, it becomes difficult to uniformly mix the coating agent in the blended coal, and at this time, the coating agent is unevenly distributed in the blended coal. For this reason, the softening and melting of the blended coal and the expansion of the coating agent become uneven, and the strength of the coke is lowered. Therefore, in this embodiment, the surface of the coke raw coal is coated to suppress the above-mentioned uneven distribution. At this time, it is effective to coat low-grade coal having poor softening and melting characteristics.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention.

[Preparation of coating agent]
Coal A (brown coal) having a moisture content of 30% by weight and methylnaphthalene were mixed, and an extraction process was performed using an autoclave at a temperature of 360 ° C., a pressure of 2 MPa, and a time of 1 hour. After extraction, an extract (a mixed solution of a coating agent and methylnaphthalene) was collected by solid-liquid separation, and methylnaphthalene was distilled off from the extract to obtain coal B (coating agent).

[Coal coating]
Coal A and 5% by weight, 10% by weight, 12% by weight or 20% by weight of coal B of coal B were stirred and mixed with methyl naphthalene at 360 ° C. to obtain a slurry. Methylnaphthalene was removed from this slurry by distillation to obtain Coal A coated with Coal B.

  The following oxidation reaction test and moisture absorption test were performed in order to investigate the pyrophoric property and moisture absorption property of coal A coated with coal B obtained by the above method.

[Oxidation reaction test]
After the coal A coated with the coal B was finely pulverized, it was closely packed in the cell, and then heated to 110 ° C. by flowing heated nitrogen into the cell. Immediately, the inflowing gas was switched to air to cause an oxidation reaction. At this time, the temperature change while the temperature of the packed coal A rose to 200 ° C. was recorded. As a comparison, this test was also conducted on Coal A and Coal B. A graph based on the test results is shown in FIG.

  In the oxidation reaction test, it is determined that the shorter the time for temperature rise to 200 ° C., the faster the oxidation rate and the higher the spontaneous ignition. As a result, coal A which has not been subjected to coating treatment has the highest temperature rise due to oxidation, and it took 78 minutes to rise to 200 ° C. Subsequently, coal A coated with 5% by weight of coal B (200 ° C. arrival time: 90 minutes), coal A coated with 10% by weight of coal B (200 ° C. arrival time: 115 minutes), and 20% by weight of coal B were coated. Coal A (200 ° C. arrival time: 117 minutes). That is, as the coating amount increased, the temperature rise gradually decreased, and the oxidation reaction was greatly suppressed by the coating of extracted coal.

[Hygroscopic test]
Coal A, Coal B, and Coal A coated with 12% by weight of Coal B were vacuum dried at 100 ° C. to obtain each dry coal having a moisture content of 0%. Each coal was put into a desiccator having a relative humidity of approximately 100%, and the moisture content absorbed by each coal was measured.

  A graph based on the results of the moisture absorption test is shown in FIG. Coal A absorbed moisture up to about 12%, equivalent to the constant moisture content of coal A, but coal A coated with coal B absorbed only about half of coal A. Since the extracted coal B has no pores, it hardly absorbs moisture.

Claims (8)

An extraction step of mixing the non-hydrogen-donating solvent and the coating agent raw coal, and extracting the soluble component of the raw coal into the solvent;
A solid-liquid separation step for separating the extraction residue and the extract after the extraction step;
The coating agent for coal which consists of the said soluble component contained in the said extract liquid isolate | separated by the method which has these. A modified coal having coal and a coating layer covering the surface of the coal,
The modified coal which the said coating layer consists of the coating agent for coal of Claim 1.   The modified coal according to claim 2, wherein the coal covered by the coating layer is an extraction residue separated in the solid-liquid separation step.   The modified coal according to claim 2 or 3, wherein the modified coal is coke raw coal. An extraction step of mixing the non-hydrogen-donating solvent and the coating material raw coal, and extracting the soluble component of the coal into the solvent;
A solid-liquid separation step for separating the extraction residue and the extract after the extraction step;
The manufacturing method of the coating agent for coal which has this.   The manufacturing method of the modified coal which coats the coal coating agent manufactured by the method of Claim 5 on the coal surface.   The method for producing modified coal according to claim 6, wherein the coal to be coated is an extraction residue separated in the solid-liquid separation step.   The method for producing modified coal according to claim 6 or 7, wherein the modified coal is coke raw coal.

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