JP5444151B2 - Solid fuel - Google Patents

Description

The present invention relates to a modified solid fuel you a low-grade coal as a raw material.

The solid fuel is preferably used as a fuel for thermal power generation, for example.
Bituminous coal is currently used as a fuel for thermal power generation, but bituminous coal production is increasing year by year, and bituminous coal is depleted. Therefore, effective use of low-grade coal as an alternative is an urgent issue.

  Low-grade coal has a low calorific value and is pyrophoric, so its use is limited. However, a modified lignite process (hereinafter referred to as UBC process) is used as one of means for effectively using this. Until now, several processes for reforming low-grade coal have been developed, but many of them are pyrolytic substances because the processing conditions are high temperature and high pressure and the equipment cost is high, or the chemical change of low-grade coal is accompanied. It was difficult to put it into practical use because of the large wastewater treatment burden caused by the generation of wastewater containing a large amount of wastewater.

  As the UBC process, the applicant of the present invention uses low-grade coal as a raw material, and contains mixed oil containing heavy oil and solvent oil in the pores. A solid fuel having a weight ratio of 0.5% to 30% has already been disclosed (Patent Document 1). In the solid fuel of Patent Document 1, the spontaneous combustion of low-grade coal is suppressed by removing moisture in the pores of low-grade coal and attaching heavy oil to the surface in the pores to cover the active sites. At the same time, high calorie is realized by including heavy oil in low-grade coal. By dissolving the heavy oil in the solvent oil and reducing the viscosity, the filling of the heavy oil into the pores is performed satisfactorily, thereby realizing active point coating and high calorieization in the pores. ing.

  By the way, powdered reformed coal is rarely consumed as fuel as it is, and is usually transported to a consumption place (for example, a thermal power plant) after being compression-molded into massive coal. When the strength of the massive coal is low, cracking or pulverization occurs during transportation or during unloading operations, and a part of the product is lost, and there is a concern about an increase in pyrophoricity. Therefore, high strength is required for the massive coal after molding.

  In addition, in order to reduce the manufacturing cost and the environmental load, it is desirable to keep the ratio of components added from the outside as low as possible or zero.

Japanese Patent No. 2776278

The present invention has been made in view of the above, and the object of the present invention is to reduce the manufacturing cost and the environmental load, and to achieve high strength for transportation and the like to suppress spontaneous ignition. An improved reformed solid fuel is provided.

  As a result of intensive studies in view of the above problems, the present inventors can not only evaporate moisture contained in low-grade coal by immersing in high-temperature oil, but also with the high-temperature oil, The non-volatile component originally contained in low rank coal was extracted, and it discovered that the said component could express the substitute function of a heavy oil component. Since the said component has the function which coat | covers the active point of a low grade coal like a heavy oil component, and suppresses spontaneous ignition, the addition rate from the exterior of a heavy oil component can be reduced.

  When further research is conducted, if the heavy oil component does not adhere to the surface of the pulverized low-grade coal, the adhesion between the pulverized coal before molding is improved, and the strength of the molded solid matter can be improved. Obtained knowledge.

The present invention has been made on the basis of the above knowledge, and the gist thereof is a solid fuel obtained by compression-molding pulverized low-grade coal, the outer surface of the low-grade coal and the inside of pores. heavy inner surface is coated with a non-volatile components contained in the low-grade coal, the content of the non-volatile components, as well as a 1% by mass relative to the solid fuel after drying, to be added from the outside of the Low-grade coal with a content of the refined oil content of less than 0.5% by mass, preferably substantially 0% by mass, based on the solid fuel after drying , and the surfaces coated with the non-volatile components adhere to each other. It is a solid fuel characterized by being molded.

  According to the present invention, the non-volatile component originally contained in the low-grade coal is dissolved by the high-temperature oil, and the component exhibits an alternative function for the heavy oil component. The manufacturing cost can be reduced and adverse effects on the environment can be suppressed. Furthermore, according to the present invention, as described above, the addition rate of the heavy oil that lowers the adhesion between pulverized coals can be reduced, thereby improving the strength of the molded solid. it can.

Therefore, according to the present invention, it is possible to provide a reformed solid fuel in which the manufacturing cost is reduced and the environmental load is reduced, and the strength is increased for transportation and the like and the spontaneous ignition is suppressed .

FIG. 1 is a process flow of a method for producing a reformed solid fuel according to the present invention. FIG. 2 is a schematic diagram showing an example of a reformed solid fuel production apparatus for carrying out the reformed solid fuel production method of the present invention. FIG. 3 is a graph for the non-volatile components of coal dissolved in kerosene. FIG. 4 shows a process flow in a steady state. FIG. 5 is a graph showing the relationship between the mass fraction of heavy oil (specifically asphalt) (ratio of anhydrous carbon) [mass%] and the strength of the molded product [kg weight].

Hereinafter, a method for producing a reformed solid fuel according to the present embodiment and a reformed solid fuel produced by the method will be described in detail with reference to the drawings. However, the following embodiments are illustrative of the present invention and are not limiting. In addition, in each figure, about the common member and component, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

(Embodiment 1)
In the method for producing a reformed solid fuel according to the present embodiment , low-grade coal is pulverized, the pulverized low-grade coal is mixed with a solvent oil to prepare a slurry, and the slurry is heated to the boiling point or higher of water. Then, in the method for producing a solid fuel in which moisture contained in the slurry is evaporated, solvent oil is separated from the slurry to produce pulverized coal, and the pulverized coal is compression-molded, the slurry is heated to a boiling point or higher of water. By extracting the non-volatile components contained in the low-grade coal with the solvent oil, and further covering the outer surface of the low-grade coal and the inner surface in the pores with the extracted non-volatile components, The ratio of the heavy oil added from the above is less than 0.5% by mass, preferably substantially 0% by mass, based on the solid fuel after drying (ie, to the ratio of anhydrous carbon). .

According to the method for producing a solid fuel according to the present embodiment, the oil mixed with the pulverized low-grade coal functions as a solvent oil, and the non-volatile components originally contained in the low-grade coal are extracted by the high-temperature oil. Since the non-volatile component exhibits an alternative function of the heavy oil component, the addition rate of the heavy oil component from the outside can be reduced. Moreover, although the amount of heavy oil added is reduced, spontaneous ignition can be suppressed as in the case of adding heavy oil. Furthermore, according to the manufacturing method of the solid fuel which concerns on this invention, since the addition rate of the heavy oil component which reduces the adhesion of pulverized coal can be reduced, the intensity | strength of the shape | molded solid substance can be improved. .

FIG. 1 is a process flow of a method for producing a reformed solid fuel according to the present embodiment . A method for producing a reformed solid fuel according to the present embodiment will be described in detail with reference to FIG. FIG. 2 is a schematic diagram showing an example of a reformed solid fuel production apparatus for performing the reformed solid fuel production method of the present embodiment . The method for producing a reformed solid fuel according to the present embodiment includes a low-grade coal pulverization / slurry preparation step, a dehydration step, a solid-liquid separation step, and a compression molding step. In addition, you may further provide the cooling process which cools the dried solid content between a solid-liquid separation process and a compression molding process.

Here, the slurry preparation step of the low-grade coal after pulverization corresponds to the mixing section in the process flow of FIG. 1 and is performed in the mixing tank 1 of the reformed solid fuel production apparatus of FIG. Further, the dehydration step corresponds to the dehydration unit in the process flow of FIG. 1 and is performed in the evaporator 7 and the gas-liquid separator 5 of the manufacturing apparatus of FIG. Further, the solid-liquid separation step corresponds to the solid-liquid separation unit (mechanical separation and heating separation) in the process flow of FIG. 1, and the mechanical solid-liquid separator (centrifugal separator) 10 of the manufacturing apparatus of FIG. 11 and dryer 12. The compression molding step corresponds to a molding unit in the process flow of FIG. 1 and is performed in a compression molding machine (not shown) of the manufacturing apparatus. The reformed solid fuel production apparatus for carrying out the reformed solid fuel production method of the present embodiment includes a mixing tank 1 for preparing a raw slurry by mixing a mixed oil containing a solvent oil with low-grade coal, and this raw material. An evaporator 7 and a gas-liquid separator 5 for evaporating the slurry; a mechanical solid-liquid separator (centrifuge) 10 for separating the slurry subjected to the moisture evaporation process into a solid-liquid separator; a screw press 11 and a dryer 12; A compression molding machine (not shown) that compresses and molds the dried powdered solid fuel to produce the molded solid fuel.
Hereinafter, each step will be described in detail.

1. Low-grade coal pulverization / slurry preparation process As shown in FIGS. 1 and 2, after pulverizing the raw low-grade coal, this is supplied to the mixing section, that is, the mixing tank 1, and the low-grade coal pulverized in the mixing tank 1 Grade coal is mixed with oil containing solvent oil to prepare a raw slurry. As the solvent oil to be mixed with the low-grade coal, various oils can be used as long as the non-volatile components contained in the low-grade coal can be extracted. The solvent oil is preferably a light boiling oil from the viewpoints of affinity with non-volatile components and heavy oil, handling as a slurry, ease of entry into pores, etc., but stable at the water evaporation temperature. Considering the properties, it is recommended to use petroleum oils having a boiling point of 100 ° C. or higher, preferably 400 ° C. or lower. Examples of this petroleum oil include kerosene, light oil, and heavy oil, while coal liquefied oil may be used. Kerosene can be preferably used.

  Here, heavy oil may be mixed with the solvent oil, but the amount of heavy oil added by adding oil to the mixing tank 1 is determined by solid fuel (cake obtained by solid-liquid separation is dried by a dryer). The amount of heavy oil adhering to the low-grade coal (modified coal) on a dry basis in this solid fuel, that is, less than 0.5% by mass in the ratio of anhydrous coal However, it is important to adjust so that it is preferably substantially 0% by mass.

  Further, as shown in FIG. 1, the oil discharged from the dehydrating unit, the solid-liquid separation unit (mechanical separation) or the solid-liquid separation unit (heating separation) is circulated as a circulating oil toward the mixing unit, and this circulating oil A solvent oil and a heavy oil may be added. In this case as well, the amount of heavy oil added is the same as described above, and the amount of heavy oil attached to the solid fuel (the cake obtained by solid-liquid separation is evaporated using a dryer) It is important to adjust to a low-grade coal (modified coal) on a dry basis, that is, to a ratio of anhydrous carbon to less than 0.5% by mass, preferably substantially 0% by mass.

  In the present invention, low-grade coal is a coal that contains a large amount of water and is desired to be dehydrated. For example, it means coal containing at least 20% by mass of moisture on a dry basis. Of course, the low-grade coal may include high-grade coal. Examples of such low-grade coal 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 Banco coal, Binungan coal, Samarangau coal, and the like. The low-grade coal is not limited to those exemplified above, and any low-grade coal containing a large amount of moisture and desired to be dehydrated is included in the low-grade coal according to the present invention.

  In the present invention, the non-volatile component is a non-volatile oil originally contained in the low-grade coal, and after this extraction, covers the outer surface of the low-grade coal, and the inner surface in the pores. It covers. Thus, since the active site in the pores of the low-grade coal is covered with the non-volatile component, the non-volatile component can suppress spontaneous ignition. Examples of such non-volatile components include aromatic high-molecular organic compounds.

  In the present invention, the heavy oil is a heavy oil that does not substantially exhibit a vapor pressure even at 400 ° C., such as a vacuum residue oil, or an oil containing the heavy oil. Similar to the property component, it has a function of suppressing spontaneous ignition by covering active sites in the pores of low-grade coal. Examples thereof include petroleum asphalt, natural asphalt, aliphatic polymer organic compound, aromatic polymer organic compound, and the like.

  In the present invention, the solvent oil is an oil that dissolves the heavy oil and can reduce the viscosity of the heavy oil, thereby facilitating the impregnation of the low-grade coal into the pores, Furthermore, non-volatile components contained in the low-grade coal can be extracted. Further, the solvent oil can dissolve the non-volatile components and reduce the viscosity thereof, thereby facilitating the impregnation of the low-grade coal into the pores.

  However, the heavy oil content is preferably as small as possible in order to reduce the mechanical strength of the compression-molded solid fuel itself when the powder-form solid fuel is compression-molded. As described above, the amount of heavy oil added is determined by the amount of heavy oil deposited on the solid fuel (the cake obtained by solid-liquid separation being evaporated with a dryer) based on the dry base in the solid fuel. It is preferable to adjust so as to be less than 0.5% by mass, preferably substantially 0% by mass with respect to the low-grade coal (modified coal). Here, FIG. 5 shows the relationship between the mass fraction of heavy oil (specifically, asphalt) (ratio of anhydrous carbon) [mass%] and the strength of the molded product [kg weight]. The horizontal axis represents the mass fraction of heavy oil (specifically asphalt) (ratio of anhydrous carbon) [mass%], and the vertical axis represents the strength of the molded product [kg weight]. As shown in FIG. 5, if the amount of heavy oil attached to the solid fuel is 0% by mass to 0.5% by mass, the strength of the solid fuel after molding may be about 68 kg to about 87 kg. it can. In particular, when the adhesion amount is 0% by mass, the strength of the solid fuel after molding is about 87 kg, which is preferable because the greatest strength can be obtained. If the molded solid fuel is pulverized, the chance of contact with the air at the active point of the solid fuel increases, and there is a concern about the increase in spontaneous ignition. However, as described above, the amount of heavy oil deposited is 0% by mass to 0%. If the strength of the molded solid fuel is increased to 0.5% by mass, spontaneous ignition can be prevented.

The type of the mixing tank according to the present embodiment is not particularly limited, and various types can be used, but it is usually preferable to use an axial flow type stirrer or the like.

  Through the low-grade coal pulverization / slurry preparation step, the raw slurry can be prepared by mixing the pulverized low-grade coal and oil containing solvent oil.

2. Dehydration process The raw material slurry obtained as described above is conveyed to the preheaters 3 and 4 by the pump 2 and preheated by the preheaters 3 and 4. Thereafter, the temperature of the raw material slurry is raised by the evaporator 7. In the evaporator 7, dehydration in oil is performed by pressure heating to 1 to 40 atm (preferably 2 to 5 atm) and 100 to 250 ° C. (preferably 120 to 160 ° C.). In the evaporator 7, the raw material slurry is heated to the boiling point or higher of water as described above, whereby water vapor is removed and the non-volatile components contained in the low-grade coal are caused by the solvent oil contained in the raw material slurry. Extracted. Thus, since the non-volatile component contained in the low-grade coal is extracted and the non-volatile component substitutes for the function of the heavy oil component, the amount of the heavy oil component to be added can be reduced as described above. it can.

  In this way, the raw material slurry is conveyed to the gas-liquid separator 5, and the water content of the raw material slurry is removed as vapor by the gas-liquid separator 5. After separating the water vapor, the slurry is withdrawn from the bottom and conveyed by the pump 6 in the direction of the centrifuge 10. A part is branched from the middle of the transfer line, the temperature is raised through the evaporator 7, and then returned to the gas-liquid separator 5. On the other hand, the vapor phase obtained by gas-liquid separation in the water vapor generated in the evaporator 7 is pressurized through the compressor 8, and the slurry is heated in the evaporator 7 by the thermal energy to perform dehydration in oil. This gas phase component is subsequently transferred to the preheater 3 and used as a preheat source for the raw slurry, and then oil / water is separated by the oil / water separator 9 and the water is discarded. The oil recovered by this oil / water separation is not so much, but is returned to the mixing tank 1 and reused.

  In the dehydration process, since the dehydration process is performed, it is necessary to heat the raw slurry to the boiling point of water or more, and further, the non-volatile components are extracted and extracted by the solvent oil contained in the raw slurry. Therefore, it is preferable to heat the raw material slurry to 100 ° C. or higher. In order to evaporate water at normal pressure, heating at a minimum of 100 ° C. is required. However, in order to reduce the size of the apparatus, it may be operated at a pressure higher than normal pressure (the volume of the gas phase is reduced). ). Further, in order to make the size of the compressor a reasonable size, the process pressure may be increased from the normal pressure. When pressurized, the boiling point of water rises, so the heating temperature needs to be 100 ° C. or higher. For example, when operating in a pressurized state of 0.4 MPa, it is necessary to evaporate water by heating to 145 ° C. or higher. On the other hand, if the temperature is increased more than necessary, not only water but also solvent oil will be evaporated. In this process, it is necessary to reduce the evaporation of the solvent oil as much as possible. Therefore, it is rational to operate at a temperature that is several degrees higher than the boiling point of water under the operating pressure. In addition, from the viewpoint of extracting non-volatile components of coal, a higher temperature is preferable.

The type of the evaporator 7 according to the present embodiment is not particularly limited, and various types can be used. For example, a heating system, a decompression system, or heating and decompression can be used. The thing of a system etc. are mentioned. For example, an evaporator such as a flash evaporation type, a coil type, or a forced circulation type vertical tube type can be used. Usually, it is preferable to use a forced circulation type evaporator attached with a heat exchanger.

  As described above, the water content contained in the low-grade coal can be evaporated by the dehydration step, thereby removing water vapor, and the non-volatile nature contained in the low-grade coal due to the solvent oil contained in the raw slurry. Ingredients are extracted.

3. Solid-Liquid Separation Step As described above, after the moisture evaporation treatment, the slurry subjected to the moisture evaporation treatment is conveyed to a solid-liquid separation section (mechanical separation), and solid-liquid separation is performed by a mechanical solid-liquid separator. The type of the mechanical solid-liquid separator is not particularly limited, and various types can be used. If an example is shown, a centrifuge, a press, a sedimentation tank, a filter etc. will be mentioned. In the present embodiment, concentration by the centrifuge 10 and compression by the screw press 11 are first performed. However, only the centrifuge or only the screw press can be used, or the centrifuge is replaced by sedimentation. Separation may be employed, and vacuum filtration may be employed instead of pressing. The oil obtained by solid-liquid separation may be returned to the mixing tank 1 as a circulating oil.

The solid component (cake) thus separated is conveyed to a solid-liquid separation unit (heated separation) and heated while flowing a carrier gas in the dryer 12 to evaporate the oil component, thereby obtaining a solid fuel.
In this heat separation step, the coal surface and the coal pores are coated with non-volatile components. That is, while the solvent oil component evaporates, the non-volatile components (heavy oil component) contained in the coal do not evaporate, and therefore remain on the surface and pores of the coal.
For this drying, a fluidized bed method or a rotary dryer method is recommended. From here, the oil carried out by the carrier gas and separated may be sent to the condenser 13, recovered as an oil component, and then returned to the mixing tank 1 as a lubricating oil.

  As described above, in the solid-liquid separation step, the slurry is solid-liquid separated by a mechanical solid-liquid separator, and the oil contained in the solid is evaporated in a dryer, thereby obtaining a powdered solid fuel. Can do.

4). Compression Molding Process The powdered solid fuel obtained as described above is sent from the dryer to the molding unit and is compression molded by a compression molding machine (not shown) to become a molded solid fuel. Examples of this compression molding machine include a tableting molding machine (tabletting) and a double roll molding machine (roll press), but it is usually preferable to use a double roll molding machine. By the compression molding step, a compacted molded solid fuel can be produced.

  According to the above method, despite the decrease in the amount of heavy oil added, spontaneous ignition can be suppressed as in the case of adding heavy oil, and the strength of the molded solid matter is improved. Can do.

Example 1: About the nature of non-volatile components contained in low-grade coal When coal is dehydrated in oil, non-volatile heavy oil such as asphalt is allowed to coexist to make the pores of coal Has been reported to effectively adsorb asphalt and suppress spontaneous ignition (Japanese Patent No. 2776278).

  The present inventors consider that some of the non-volatile components of coal are dissolved and extracted in high-temperature oil, so that the dissolved non-volatile components may exhibit an asphalt substitute function. It was.

Therefore, the solubility of coal (Indonesian brown coal) in high-temperature solvent oil (kerosene) was measured. The procedure is as follows.
1) Pulverized charcoal (1 mm diameter or more is 10% by mass or less) and kerosene were mixed in a round bottom flask at room temperature.
2) The round bottom flask was placed in a heater and gradually heated, and the sample was heated to 140 ° C. over 2 hours. At this time, nitrogen gas of 200 cm ³ / min was supplied to make the inside of the flask in an inert atmosphere. During this time, the water in the evaporated coal was extracted as vapor from the top of the round bottom flask, condensed in a cooling tube, and extracted out of the system as liquid (water). The sample in the round bottom flask was held at 140 ° C. for 1 hour.
3) Next, the sample in the round bottom flask was subjected to pressure filtration while being in a high temperature state (pressurization with 0.1 MPa of nitrogen gas) to separate the solid phase and the liquid phase.
4) After the liquid phase after separation is cooled once, it is poured into a flask of a distillation apparatus, vacuum distillation is performed under the following conditions to evaporate kerosene and take it out of the system, and evaporate residue, that is, coal dissolved in kerosene. Non-volatile components were recovered.
Pressure: 10mmHg
Rate of temperature increase: 2 ° C./min Final temperature: 159 ° C. (After reaching the final temperature, hold until no steam is generated: 60 minutes)

  FIG. 3 shows the measurement results. Here, s / c represents the ratio between the weight of kerosene charged and the weight of coal (dry basis). The coal weight reduction rate represents the weight fraction of components dissolved in kerosene with respect to the dry coal weight charged. As shown in FIG. 3, it was found that at least 1% of the raw coal was dissolved in 140 ° C. kerosene.

  In addition, it turned out that at least 1% of raw material coal melt | dissolves in 140 degreeC kerosene similarly with another coal type.

  The component dissolved in kerosene from coal is a non-volatile heavy oil, and its properties are very similar to those of heavy oil such as asphalt added from the outside in the prior art. It has been found that a low-grade coal reforming process can be established without adding a quality oil.

Example 2: Process Flow Subsequently, as an example, a process flow in a steady state is shown in FIG. 4 together with a material balance. The quantities in FIG. 4 indicate mass flow rates. Here, DC is anhydrous carbon, SC is a non-volatile component contained in coal, W is water, and O is kerosene. About 1% of the raw coal is soluble in kerosene, and its concentration increases with time in the circulating kerosene. In the dewatering section, 1% of coal is dissolved in hot kerosene. On the other hand, in the solid-liquid separation part (mechanical separation), a part of kerosene remains on the surface and pores of coal. The kerosene contains about 3% of the kerosene soluble component of coal, that is, the non-volatile component contained in the coal, so that kerosene is evaporated and separated in the next solid-liquid separation part (heated separation). In contrast, kerosene soluble components of coal that are non-volatile will remain on the surface and pores of the coal.

  In the prior art, the addition of heavy components (asphalt) aims to suppress spontaneous ignition of product charcoal. Therefore, the ratio of the mass component remaining in the product is set to 1% by mass, for example. Therefore, in order to obtain a product of equivalent quality, 1% by mass of a non-volatile component soluble in kerosene in coal remains in the product. For this purpose, in the mechanical solid-liquid separation step (centrifugation) in FIG. 4, the weight ratio of anhydrous carbon (DC) contained in the solid phase side and non-volatile component (SC) soluble in kerosene is 99: 1. What should be done. At this time, the mass ratio of the non-volatile component and kerosene in the slurry supplied to the mechanical solid-liquid separation step (centrifugation) is 4.5: 157, that is, approximately 3: 100. Therefore, if the ratio of anhydrous carbon and kerosene contained on the solid phase side is about 99:33 (99: 34.5 in FIG. 4), the non-volatile nature contained in anhydrous coal, kerosene and coal. The weight ratio with the components is 99: 33: 1. The solid phase containing kerosene is separated by vaporizing most of kerosene in the next heating step (drying step), but the non-volatile components soluble in kerosene are heavy and are not separated. It remains on the coal surface as it is. In a continuous centrifuge, the main parameters that determine the separation performance between the solid phase and the liquid phase are the rotational speed and the average residence time. The larger the number of revolutions and the longer the average residence time, the fewer liquid phases remain in the solid phase. There are various sizes and types of continuous centrifuges, and the rotational speed and average residence time for obtaining the desired solid-liquid separation performance are different from each other and cannot be determined unconditionally. By performing solid-liquid separation as described above, approximately 1% by mass of a non-volatile component can be left in the anhydrous carbon, and the addition of heavy oil can be preferably eliminated.

Example 3 Regarding Strength of Molded Solid Fuel According to the prior art (Japanese Patent No. 2776278), it is said that the content of heavy oil is added at least 0.5% by mass with respect to the mass ratio of anhydrous carbon.

  Select asphalt as heavy oil, change asphalt mass fraction (ratio of anhydrous coal), modify low-grade coal (Indonesian brown coal), then double roll molding machine (Furukawa Otsuka Iron Works) K-205) produced bean charcoal solid fuel. The rotation speed of the double roll molding machine was 8 rpm. The strength was measured with a crushing strength meter (XA-500 manufactured by Furukawa Otsuka Iron Works Co., Ltd.).

  The result is shown in FIG. FIG. 5 is a graph showing the relationship between the mass fraction of heavy oil (specifically asphalt) (ratio of anhydrous carbon) [mass%] and the strength of the molded product [kg weight]. The horizontal axis represents the mass fraction of heavy oil (specifically asphalt) (ratio of anhydrous carbon) [mass%], and the vertical axis represents the strength of the molded product [kg weight]. As shown in FIG. 5, if the amount of heavy oil attached to the solid fuel is 0% by mass to 0.5% by mass, the strength of the solid fuel after molding may be about 68 kg to about 87 kg. it can. In particular, when the adhesion amount is 0% by mass, the strength of the solid fuel after molding becomes about 87 kg weight, and the greatest strength is obtained. If the molded solid fuel is pulverized, the chance of contact with the air at the active point of the solid fuel increases, and there is a concern about the increase in spontaneous ignition. However, as described above, the amount of heavy oil deposited is 0% by mass to 0%. If the strength of the molded solid fuel is increased to 0.5% by mass, spontaneous ignition can be prevented. From FIG. 5, it was found that the lower the asphalt mass fraction, the higher the strength of the molded product, especially 0% by mass, that is, the highest strength when no asphalt is added. In order to increase the strength of the molded product, it is preferable that the adhesion between pulverized coal before molding is high, but it is considered that the adhesion is reduced by adsorbing asphalt on the surface of the coal. Although the detailed mechanism is unknown, it can be considered that the affinity (adhesion) with coal (aromatic) is inferior because asphalt is derived from petroleum (aliphatic).

DESCRIPTION OF SYMBOLS 1 Mixing tank 2 Pump 3 Preheater 4 Preheater 5 Solid-liquid separator 6 Pump 7 Evaporator 8 Compressor 9 Oil-water separator 10 Centrifugal separator 11 Screw press 12 Dryer 13 Condenser 14 Pump 15 Cooler 16 Heater

Claims (2)

Solid fuel made by compression molding of pulverized low-grade coal,
The outer surface of the low-grade coal and the inner surface in the pores are coated with non-volatile components contained in the low-grade coal,
The content of the non-volatile components, as well as a 1% by mass relative to the solid fuel after drying, the content of the heavy oil to be added from the outside, 0.5 mass relative to the solid fuel after drying Solid fuel, characterized in that it is formed by adhering and molding low-grade coal whose surface is less than% and whose surface is coated with the non-volatile component.   2. The solid fuel according to claim 1, which does not substantially contain the heavy oil component.

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