JP2011111529A - Ignition-resistant coal and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide ignition-resistant coal satisfactorily restraining oxygen gas from being absorbed thereon and a method for producing the ignition-resistant coal at a low price. <P>SOLUTION: The method for producing the ignition-resistant coal comprises the steps of: dehydrating raw coal to obtain the modified coal; and absorbing carbon dioxide on the modified coal. The ignition-resistant coal is characterized in that the absorbed amount of the carbon dioxide is 0.003-0.100 NmL/g-coal. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an ignition resistant coal excellent in spontaneous ignition resistance and a method for producing the same.

  Coal is widely used as a fuel for thermal power generation and boilers, a gasification raw material for hydrogen production, and a raw material for chemical products. As such coal, dehydrated coal fuel has attracted attention from the viewpoint of combustion efficiency and environmental measures.

  However, since dehydrated coal has reduced moisture, for example, when it is stacked and placed during transport or storage, heat generation has been a problem. Heat generation is caused by the fact that coal fuel absorbs oxygen gas and undergoes an oxidation reaction, and when heat generation is severe, it is known that smoke and spontaneous combustion occur. Various measures for preventing this have been proposed, but none of these measures can sufficiently suppress the oxygen absorption of coal fuel, and a method that can be implemented industrially at low cost is not known. The problem of ignition resistance was particularly remarkable when lignite was used as the coal raw material.

  An object of this invention is to provide the ignition-resistant coal by which absorption of oxygen gas can fully be suppressed, and the method of manufacturing such coal cheaply.

  The present invention relates to a method for producing an ignition-resistant coal, wherein carbonaceous gas is absorbed into the modified coal after the coal raw material is dehydrated to obtain the modified coal.

  The present invention also relates to an ignition-resistant coal, wherein carbon dioxide absorption is 0.003 to 0.100 NmL / g-coal.

Since the ignition resistant coal of the present invention absorbs carbon dioxide, absorption of oxygen gas having an oxidizing action is sufficiently suppressed. As a result, the oxidation rate of coal can be effectively reduced. Therefore, ignition resistant coal has sufficient spontaneous ignition resistance.
Carbon dioxide gas to be absorbed by the reformed coal is contained at a high concentration in, for example, boiler flue gas, so that it can be procured at low cost. Therefore, the ignition resistant coal of the present invention can be produced industrially at low cost. Moreover, since carbon dioxide is inert and harmless, no problem arises if carbon dioxide is released from ignition resistant coal.
The ignition resistant coal of the present invention has almost no difference in combustion efficiency compared with the reformed coal conventionally used as coal fuel.

It is a process flow figure showing one embodiment for obtaining reformed coal by a dehydration method in oil. It is a schematic diagram which shows one Embodiment of a solid-liquid separation process. It is a schematic diagram which shows one Embodiment of a final drying process. It is a schematic diagram which shows one Embodiment of the apparatus for obtaining a reformed coal according to the process flowchart shown in FIG.

  The ignition resistant coal of the present invention can be produced by removing at least moisture from a coal raw material to obtain a modified coal once, and then allowing the modified coal to absorb carbon dioxide.

  The modified coal that absorbs carbon dioxide gas is coal obtained by removing at least moisture from the coal raw material, and can be obtained, for example, by dehydration treatment described in detail later.

  In the present specification, the reformed coal refers to coal after removing moisture from the coal raw material and before carbon dioxide absorption treatment. Specifically, the modified coal has a water content of 15% by weight or less, usually 0.5 to 15% by weight, preferably 0.5 to 10% by weight, more preferably 0.5 to 8% by weight. belongs to. The modified coal that satisfies the moisture content described above is generally easily ignited. However, in the present invention, by performing carbon dioxide absorption treatment on such modified coal, ignition resistance can be effectively imparted. In the present invention, so-called hyper coal (ashless coal) from which not only moisture but also ash is removed may be used as the modified coal.

  In this specification, the water content uses a value measured by the method described in JIS M8812.

  The modified coal may be subjected to a carbon dioxide absorption treatment in the form of a powder, or may be subjected to a carbon dioxide absorption treatment in the form of a molded body having a desired shape. From the viewpoint of carbon dioxide absorption efficiency, a preferred modified coal form is powder.

  When the modified coal is subjected to carbon dioxide absorption treatment in a powder form, the particle diameter of the modified coal particles is not particularly limited, but the particle diameter of 100% of the particles is preferably 50 mm or less, more preferably the particles 80% or more of the particle diameter is 3 mm or less. The average particle diameter of the modified coal particles is 3 mm or less, particularly preferably 0.05 to 3 mm, and preferably 0.05 to 2.0 mm, more preferably 0, from the viewpoint of the balance between carbon dioxide absorption efficiency and economy. .1 to 0.5 mm.

  When the modified coal is used in the form of a molded body, the shape is not particularly limited, and may be, for example, a so-called briquette shape, pillow shape, almond shape, or the like.

<Carbon dioxide absorption process>
The carbon dioxide absorption process is a process in which carbon dioxide is absorbed by the modified coal. By absorbing carbon dioxide into the modified coal, the absorption of oxygen gas into the coal is sufficiently suppressed, so that the oxidation rate of the coal can be effectively reduced, and as a result, the treated coal is sufficient Exhibits spontaneous ignition resistance.

  The method for absorbing carbon dioxide into the modified coal is not particularly limited as long as the amount of carbon dioxide absorption described below is achieved. For example, a method of holding the modified coal in a carbon dioxide-containing atmosphere can be mentioned. Absorption includes not only the concept that carbon dioxide is taken into the pores of coal, but also the concept that carbon dioxide is adsorbed on the coal surface and a physical or chemical bond is formed between the coal and carbon dioxide. Mean.

  The atmosphere containing carbon dioxide is brought about by an atmosphere gas containing carbon dioxide. The atmosphere gas containing carbon dioxide may contain other gases other than carbon dioxide within a range that does not inhibit the absorption of carbon dioxide into the reformed coal. Examples of such other gas include nitrogen gas and water vapor. It is preferable that the atmospheric gas does not contain oxygen gas, but oxygen gas must not be strictly excluded, and the present invention achieves the carbon dioxide gas absorption amount described below for the carbon dioxide absorbed coal. This does not prevent the oxygen gas from being contained in the atmospheric gas within the range. For example, the atmospheric gas may contain oxygen gas at a concentration of 10% by volume or less.

  A preferred carbon dioxide-containing atmosphere consists of carbon dioxide and nitrogen gas.

  The carbon dioxide content in the carbon dioxide-containing atmosphere is usually 0.1% by volume or more, particularly 0.5% by volume or more, and preferably 0.5 to It is 20 volume%, More preferably, it is 5-20 volume%, More preferably, it is 8-15 volume%.

  The temperature (treatment temperature) of the carbon dioxide-containing atmosphere is usually 10 to 220 ° C., and preferably 15 to 210 ° C., more preferably 20 to 170 ° C., from the viewpoint of the balance between carbon dioxide absorption efficiency and economy. More preferably, it is 20-100 degreeC, Most preferably, it is 20-80 degreeC.

  The holding time (treatment time) in the carbon dioxide-containing atmosphere is not particularly limited as long as the carbon dioxide absorption amount described below is achieved, and is usually 5 minutes or more, and the balance between carbon dioxide absorption efficiency and economic efficiency From the viewpoint, it is preferably 10 to 60 minutes, more preferably 20 to 40 minutes.

  The carbon dioxide absorption treatment is preferably performed under pressure of about 0.1 to 1 MPa from the viewpoint of carbon dioxide absorption efficiency, but may be performed under normal pressure.

  The carbon dioxide absorption treatment may be performed in a continuous manner, or may be performed in a so-called batch manner, and is preferably performed in a continuous manner from the viewpoint of manufacturing cost during mass production.

  When the carbon dioxide absorption treatment is performed continuously, for example, using a fluidized bed type absorption device, the reformed coal is conveyed at a predetermined pressure and a predetermined temperature in a predetermined carbon dioxide-containing atmosphere, and reformed. Carbon dioxide absorption treatment can be performed by exposing coal to an atmosphere containing carbon dioxide.

  When performing the carbon dioxide absorption treatment in a batch manner, for example, by storing the reformed coal in a sealed container and setting the inside to a predetermined carbon dioxide-containing atmosphere, by holding it under a predetermined pressure and a predetermined temperature, Carbon dioxide absorption treatment can be performed.

The amount of atmospheric gas used varies depending on whether the carbon dioxide absorption treatment is performed in a continuous or batch manner.
For example, in the case of continuous carbon dioxide absorption treatment, the amount of atmospheric gas used is usually 1 m ³ / ton-coal or more in terms of the ratio of atmospheric gas / modified coal. From the viewpoint of balance, it is preferably 1 to 10 m ³ / ton-coal, more preferably 1 to 5 m ³ / ton-coal. In this case, the atmospheric gas may be circulated and reused continuously.
Also, for example, in the case of batch type carbon dioxide absorption treatment, the amount of atmospheric gas used is usually at least 0.5 m ³ / ton-coal in the ratio of atmospheric gas / modified coal, and the carbon dioxide absorption efficiency and economy From the viewpoint of balance with nature, it is preferably 1 to 10 m ³ / ton-coal. In this case, the atmospheric gas may be collected and reused every time the process is completed.

  The ignition resistant coal of the present invention obtained by the above carbon dioxide absorption treatment has a carbon dioxide absorption of 0.003 NmL / g-coal or more, and preferably 0.010 NmL / g-coal from the viewpoint of ignition resistance. That's it. From the viewpoint of balance between ignition resistance and production cost, the carbon dioxide absorption is preferably 0.003 to 0.100 NmL / g-coal, more preferably 0.010 to 0.100 NmL / g-coal, more preferably 0. 0.020 to 0.100 NmL / g-coal, more preferably 0.050 to 0.090 NmL / g-coal. If the carbon dioxide absorption is too small, the desired ignition resistance cannot be obtained.

The carbon dioxide absorption amount of the ignition resistant coal varies depending on the carbon dioxide absorption treatment conditions such as the carbon dioxide content, the treatment temperature, the treatment time, the treatment pressure, and the amount of the atmosphere gas used in the carbon dioxide containing atmosphere.
For example, the greater the carbon dioxide content, the greater the carbon dioxide absorption. The smaller the carbon dioxide content, the smaller the carbon dioxide absorption.
For example, as the processing temperature is lower within the above range, the amount of carbon dioxide absorption increases. The higher the treatment temperature is within the above range, the smaller the carbon dioxide absorption.
For example, the longer the treatment time, the larger the carbon dioxide absorption. The shorter the treatment time, the smaller the carbon dioxide absorption.
For example, the higher the treatment pressure, the larger the carbon dioxide absorption. The lower the processing pressure, the lower the carbon dioxide absorption.
For example, the amount of carbon dioxide absorption increases as the amount of atmospheric gas used increases. The smaller the amount used, the smaller the carbon dioxide absorption.

Carbon dioxide absorption of ignition resistant coal is a value obtained by converting the amount of carbon dioxide gas liberated when the temperature of coal is raised to 150 ° C. into the amount in a standard state (0 ° C., 1 atm) per 1 g of coal. (Nml / g-coal), specifically, a value measured by the following method is used.
A quartz tube flow reactor having an inner diameter of 10 mm and a length of 200 mm was filled with 5 g of sample, and the temperature was raised from 25 ° C. to 150 ° C. at 5 ° C./min while nitrogen gas was circulated at a rate of 20 ml / min. Hold at temperature for 30 minutes. During this period, all exhaust gas was collected, and the carbon dioxide concentration in the gas was analyzed by gas chromatography. The amount of carbon dioxide in the exhaust gas was taken as the amount of absorption and displayed in units of Nml / g-coal.

  The ignition resistant coal of the present invention obtained by the carbon dioxide absorption treatment also has a moisture content of usually 0.5 to 15% by weight. The ignition resistant coal of the present invention is excellent in ignition resistance even if the moisture content is relatively small.

<Dehydration process>
A dehydration process is a process for removing coal at least from a coal raw material, and obtaining coal (reformed coal).

  The dehydration method is not particularly limited as long as dehydration of the coal raw material can be achieved. For example, a so-called oil-in-water dehydration method, a solution extraction method, a nitrogen stream drying method, a sun drying method, and the like can be employed. A preferred dehydration method is an oil-in-water dehydration method. The dewatering method in oil can relatively effectively reduce the moisture content in coal, and the modified coal obtained by such a method is generally inferior in ignition resistance. Even if it is coal, ignition resistance can be effectively provided by the said carbon dioxide absorption process. In particular, modified coal having a moisture content reduced within the above-described range can be obtained relatively easily by the dehydration method in oil.

  A so-called hyper call method can also be employed as a dehydration method. The hyper coal method is a method of obtaining so-called hyper coal (ashless coal) by performing dehydration in an oil dehydration method and then extracting coal components with a solvent to remove ash as a solid phase.

[Dehydration method in oil]
The oil-in-water dehydration method has the following steps (A1) to (A4);
(A1) A mixing step in which a raw material slurry is obtained by mixing a coal raw material with a mixed oil containing a heavy oil component and a solvent oil component;
(A2) Evaporating step of heating the raw material slurry to advance dehydration of the coal raw material and impregnating the mixed oil into the pores of the coal raw material to obtain a dehydrated slurry;
(A3) a solid-liquid separation step of separating the reformed coal and the mixed oil from the dewatered slurry;
(A4) A step of drying the modified coal.

  Each step will be described in detail with reference to FIGS. FIG. 1 is a process flow diagram showing an embodiment for obtaining reformed coal by a dewatering method in oil. FIG. 2 is a schematic view showing an embodiment of the solid-liquid separation step. FIG. 3 is a schematic view showing an embodiment of the final drying step. FIG. 4 is a schematic diagram showing an embodiment of an apparatus for obtaining modified coal according to the process flow diagram shown in FIG.

(Mixing step (A1))
In this step, the coal raw material is mixed with a mixed oil containing heavy oil and solvent oil to obtain a raw material slurry (mixing step in FIG. 1). This step is performed in the mixing tank 2 in FIG.

  As the coal raw material, a so-called low grade coal that contains a large amount of water and is desired to be dehydrated, for example, coal containing 30 to 70% by weight of water is preferably used. Examples of such coal raw materials include lignite, lignite, subbituminous coal, and the like. For example, lignite coal includes Victoria coal, North Dakota coal, Belga coal, etc., and subbituminous coal includes West Bango coal, Binungan coal, Samarangau coal, Ecocoal coal, and the like. The coal raw material is usually used after being pulverized in advance (the pulverization step in FIG. 1). The particle diameter of the coal raw material is not particularly limited, and may be within the same range as the average particle diameter when the above-described modified coal has a powder form.

  The heavy oil component is an oil containing a heavy component or a large amount that does not substantially exhibit a vapor pressure even at 400 ° C., such as a vacuum residue oil. Therefore, if only heavy oil is used and it is attempted to heat it until it is fluid enough to enter the pores of the coal feed, the coal feed itself will undergo thermal decomposition. Further, as described above, the heavy oil used in the present invention hardly exhibits a vapor pressure. Therefore, it is impossible to vaporize the heavy oil and deposit it on a carrier gas. As a result, not only a heavy oil component is highly viscous and it is difficult to obtain a good slurry, but also has little volatility, so that the penetration into the pores is low. Therefore, it is necessary to cooperate with any solvent or dispersant.

  Therefore, in the present invention, the heavy oil component is dissolved in the solvent oil component to improve the impregnation workability and slurry forming property before use. As the solvent oil for dispersing the heavy oil, a light boiling oil is preferred from the viewpoint of affinity with the heavy oil, handling as a slurry, ease of penetration into the pores, etc. In view of the stability of the oil, it is recommended to use petroleum oil (boiling oil, light oil, heavy oil, etc.) having a boiling point of 100 ° C. or higher, preferably 300 ° C. or lower. When such a heavy oil-containing mixed oil is used, it exhibits appropriate fluidity, and therefore, penetration into pores that cannot be achieved by the heavy oil alone is promoted.

  The heavy oil-containing mixed oil as described above is (i) originally obtained as a mixed oil containing both heavy oil and solvent oil, or (b) obtained by mixing heavy oil and solvent oil. Any of the above can be used. The former (b) includes, for example, petroleum-based heavy oils; petroleum-based light oil fractions that have not been refined and contain heavy oil components, kerosene fractions, lubricating oil components; coal tar; Light oil or kerosene that contains impurities of quality oil; heat transfer oil that contains fractions that have deteriorated due to repeated use are used. As the latter (b), for example, petroleum asphalt, natural asphalt, coal-based heavy oil, petroleum-based or coal-based distillation residue, or a mixture containing many of these is mixed with petroleum-based light oil, kerosene, lubricating oil, etc. Those obtained by diluting the mixed oil of the former (A) with petroleum-based light oil, kerosene, lubricating oil, etc. are used. Asphalts are particularly suitable because they are inexpensive per se and are difficult to leave once attached to the active site.

  The content of the heavy oil in the mixed oil is usually in the range of 0.25 to 15% by weight with respect to the total amount of the mixed oil.

  The mixing ratio of the mixed oil with respect to the coal raw material is not particularly limited. Usually, the mixing ratio of the heavy oil to the coal raw material is 0.5 to 30% by weight with respect to the anhydrous coal, particularly 0.5 to 5%. % Is a reasonable range. If the mixing ratio of the heavy oil is too small, the amount of adsorption into the pores becomes insufficient, and the effect of suppressing spontaneous ignition is weakened. If the mixing ratio of heavy oil is too large, the cost of oil becomes a burden and the economy is reduced.

  Mixing conditions are not particularly limited, and usually, mixing is performed at 40 to 100 ° C. under atmospheric pressure.

  The raw material slurry obtained in the mixing step may be preheated before the evaporation step (preheating step in FIG. 1) or may not be preheated. The preheating condition is not particularly limited. When preheating is performed, the preheating process is performed by the preheater 3 in FIG.

(Evaporation process (A2))
In this step, the raw material slurry is heated to dewater the coal raw material, and the mixed oil is impregnated in the pores of the coal raw material to obtain a dehydrated slurry (evaporation step in FIG. 1). This step is performed by the evaporator 4 in FIG.

  In detail in this process, a raw material slurry is heated, for example to 100-250 degreeC. As a result, the mixed oil is replaced and attached to the empty seat portion after the moisture in the pores of the coal raw material has evaporated and evaporated. In this way, the mixed oil is attached and coated as the vaporization and evaporation of the moisture in the pores proceeds. Even if some water vapor remains, a negative pressure is formed when it condenses during the cooling process, and the heavy oil-containing mixed oil is sucked into the pores. The mixture oil is successively covered with the mixed oil containing the fine oil, and finally, almost the entire area of the pore opening is filled with the mixed oil containing the heavy oil. In addition, the heavy oil in the mixed oil is easily selectively adsorbed at the active site, and when it adheres, it is difficult to separate, and as a result, it is expected to preferentially adhere to the solvent oil. Thus, it becomes possible to lose spontaneous ignition by blocking the surface layer portion in the pores from the outside air. In addition, a large amount of water is removed by evaporation, and the heavy oil-containing mixed oil, particularly heavy oil, preferentially fills the pores, so that calorie increase as a whole coal raw material is achieved at low cost.

Heating is preferably performed under pressure, and usually 2 to 15 atmospheres is suitable.
The heating time is not generally defined because a series of steps are usually carried out by continuous operation, and it is only necessary to achieve dehydration of the coal raw material and impregnation of the mixed oil into the pores.

  Water vapor generated by heating in the evaporation step is removed. Water vapor generated / removed in this step can be recovered and increased in pressure and used as a heating source in a preheating step or an evaporation step. Further, the water vapor can be liquefied and cooled to be used as water used in the water addition step.

(Solid-liquid separation step (A3))
In the solid-liquid separation step, the reformed coal and the mixed oil are separated from the dewatered slurry (solid-liquid separation step in FIG. 1). This step is performed by the solid-liquid separator 5 in FIG.

  Various methods can be used as the separation method, and for example, a centrifugal separation method, a sedimentation method, a filtration method, a pressing method, and the like can be used. A combination of these methods can also be used. From the viewpoint of separation efficiency, it is preferable to use a centrifugal separation method.

  For example, when employing the centrifugal separation method, as shown in FIG. 2, the dehydrated slurry 11 obtained in the evaporation step is first cooled to less than 100 ° C., usually 80 to 99 ° C., with a cooler 12. Next, after the solid-liquid separation by the solid-liquid separator 5a is performed on the dehydrated slurry, the modified coal as the solid content 14 is usually sent to the final drying step 6 and dried. On the other hand, the mixed oil as the liquid component is sent to the mixing step 2 and can be circulated and used as a medium (circulating oil (CO)) for forming the raw slurry (circulation step).

(Drying step (A4))
Since the solid content (modified coal) separated in the solid-liquid separation step is usually still wet with the mixed oil, it is dried (final drying step in FIG. 1). This process is performed by the dryer 6 in FIG.

  The drying method is not particularly limited as long as the mixed oil can be evaporated and separated from the modified coal. Usually, a method using a steam tube dryer using a carrier gas such as nitrogen gas is preferable from the viewpoint of drying efficiency. In the steam tube dryer 6, for example, as shown in FIG. 3, the reformed coal cake 52 separated in the solid-liquid separation step is heated to, for example, about 200 ° C. to evaporate the oil in the cake, particularly the solvent oil. At the same time, the evaporated oil is removed from the dryer by carrier gas (CG), and the modified coal 53 is obtained. Since the modified coal is generally accompanied by the carrier gas containing the evaporated oil, the accompanying modified coal is removed by the dust collector 54. Normally, further, in the gas cooler 55, the evaporated oil is condensed by cooling, while circulating oil (CO) is circulated and sprayed, and residual reformed coal in the carrier gas is captured and removed with the circulating oil. The reformed coal and the carrier gas (CG) from which the evaporated oil is removed are circulated and heated and reused in the steam tube dryer 6. The oil (mixed oil) obtained by condensing the evaporated oil in the carrier gas can be circulated and used as a medium (circulated oil (CO)) for forming the raw slurry. The carrier gas piping from the dryer 6 to the dust collector 54 and the carrier gas piping from the dust collector 54 to the gas cooler 55 are usually provided with heaters 56 to prevent condensation of evaporated oil during carrier gas conveyance. Established.

  The dried modified coal may be cooled and molded as desired (cooling process and molding process in FIG. 1). For example, it can be cooled in the cooling step and obtained as powdered modified coal, or after cooling in the cooling step, it can be molded in the molding step and obtained as molded modified coal. In addition, the molded modified coal can be obtained by being molded in the molding process without being cooled.

<Experimental example>
The apparatus similar to that shown in FIG. 4 was continuously operated except that the centrifuge 5a shown in FIG. 2 was used as the solid-liquid separator 5 and the preheater 3 was not provided to obtain modified coal.

  Specifically, lignite (coal raw material) was pulverized with a hammer crusher to a maximum particle size of 3000 μm and an average particle size of about 150 μm, and supplied to the mixing tank 2. In the mixing tank 2, lignite coal 180 kg / hour and asphalt / kerosene oil mixture 250 kg / hour [circulated mixed oil 249 kg / hour, asphalt 1 kg / hour] are supplied to prepare a raw material slurry (80 ° C., 100 kPa). The moisture content of lignite was 42% by weight.

  The raw material slurry is supplied to the evaporator 4 (430 kg / hour) while being partially returned to the mixing tank 2 by the slurry pump SP, and is dehydrated in oil under the conditions of 160 ° C. and 300 kPa. This treatment removes moisture and forms a dehydrated slurry. The dehydrated slurry is supplied to the solid-liquid separator 5 while being partially returned to the evaporator 4 by the slurry pump SP, and is solid-liquid separated by the centrifuge 5a. In detail, in the solid-liquid separator 5, as shown in FIG. 2, the dehydrated slurry 11 is cooled to about 80 ° C. by the cooler 12, and then supplied to the centrifuge 5 a (130 ° C., 100 kPa) as a liquid component. The separated mixed oil 13 is sent to the mixing tank 2 as circulating oil (CO), and is circulated and used as a medium for forming the raw slurry. The reformed coal as the solid content 14 separated by the centrifuge is sent to the final dryer 6 and dried as shown in FIG. In detail in the final dryer 6, as shown in FIG. 3, the reformed coal cake 52 is heated to about 200 ° C. by the steam tube dryer 6 to evaporate the oil in the cake, and the evaporated oil content is obtained by the carrier gas (CG). Is removed from the dryer to obtain modified coal 53. During the continuous operation as described above, the circulation speed of the circulating oil was 40 kg / hour. The water content of the modified coal 53 was 0.8% by weight.

Next, carbon dioxide absorption treatment of the modified coal was performed. Specifically, using a fluidized bed type absorber, the reformed coal is conveyed in a predetermined carbon dioxide-containing atmosphere under a pressure of 0.1 MPa and a predetermined temperature to expose the modified coal to the carbon dioxide-containing atmosphere. did. The passage time (retention time) of the modified coal in the atmosphere was 30 minutes, and the atmosphere gas / modified coal ratio was 3 m ³ / ton-coal.
The moisture content when the modified coal was put in a pile of 6 m in height and left in the atmosphere for 1 week was 5.8% by weight treated under any conditions.

[Evaluation]
[Measurement of carbon dioxide absorption]
Carbon dioxide absorption was measured by the above-described method using the obtained coal and the modified coal not subjected to carbon dioxide absorption treatment as samples.

[Relative evaluation of spontaneous ignition resistance]
Using the obtained coal and the modified coal that was not subjected to carbon dioxide absorption treatment as a sample, relative ignition resistance was evaluated by the following method.
10 g of the sample was placed in a quartz container having an internal volume of 1000 ml, the inside was filled with air and confined, and the whole container was placed in a thermostat at 70 ° C. and held for 24 hours. After that, the gas composition inside was analyzed by gas chromatography, and the amount of absorbed oxygen was measured. The oxygen absorption amount in the modified coal that was not subjected to the carbon dioxide absorption treatment was set as 100, and the relative values were compared.
The relative value of the oxygen absorption amount is a level at which more than 90 is judged to have no ignition resistance (practical problem), and a level at which 90 or less is judged to have ignition resistance (no problem for practical use). It is. In particular, the relative value of oxygen absorption is preferably 50 or less, more preferably 30 or less, and most preferably 10 or less.

  From the experimental examples, regarding the carbon dioxide absorption treatment, the lower the treatment temperature and the higher the carbon dioxide concentration of the atmospheric gas, the more effective the improvement of spontaneous ignition resistance.

  The ignition-resistant coal of the present invention is useful as a fuel (for example, thermal power generation or boiler fuel), a gasification raw material (for example, a gasification raw material for hydrogen production), a chemical raw material, and a blast furnace blowing coal.

    2: mixing tank, 3: preheater, 4: evaporator, 5: 5a: 5b: solid-liquid separator, 6: dryer, 11: dehydrated slurry, 12: cooler, 13: liquid component (mixed oil), 14: Solid content (modified coal), 21:31:41: Water addition device, 52: Modified coal cake, 53: Modified coal, 54: Dust collector, 55: Gas cooler, 56: Heater.

Claims (7)

  A method for producing an ignition-resistant coal, comprising dehydrating a coal raw material to obtain modified coal, and then allowing the modified coal to absorb carbon dioxide.   The method for producing ignition-resistant coal according to claim 1, wherein carbon dioxide is absorbed into the modified coal so that the absorption amount is 0.003 to 0.100 NmL / g-coal.   The method for producing ignition-resistant coal according to claim 1 or 2, wherein coal combustion exhaust gas is used as carbon dioxide gas to be absorbed by the modified coal.   The moisture content of the modified coal is 0.5 to 15% by weight, The method for producing an ignition-resistant coal according to any one of claims 1 to 3. The method for producing an ignition-resistant coal according to any one of claims 1 to 4, wherein the dehydration method is a dehydration method in oil, and the method includes the following steps;
(A1) A mixing step in which a raw material slurry is obtained by mixing a coal raw material with a mixed oil containing a heavy oil component and a solvent oil component;
(A2) Evaporating step of heating the raw material slurry to advance dehydration of the coal raw material and impregnating the mixed oil into the pores of the coal raw material to obtain a dehydrated slurry;
(A3) a solid-liquid separation step of separating the reformed coal and the mixed oil from the dewatered slurry;
(A4) A step of drying the modified coal.   An ignition-resistant coal produced by the method according to any one of claims 1 to 5.   An ignition-resistant coal having a carbon dioxide absorption of 0.003 to 0.100 NmL / g-coal.

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