JP2011057750A - Solid fuel and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid fuel which has a good combustibility and can sufficiently reduce welding to an apparatus during production even if a thermoplastic is used. <P>SOLUTION: The solid fuel contains a powder obtained from coal, and a heating processed product obtained by heating a plastic. The powder contains at least one of pulverized coal prepared by pulverizing coal and a thermal decomposition product obtained by thermally decomposing the pulverized coal. The plastic contains a thermoplastic, and the heating processed product contains a re-solidified product obtained by melting the thermoplastic, followed by cooling it. The content of a volatile matter is 25-80 mass% and a content of fixed carbon is 10-70 mass%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solid fuel and a method for producing the same.

  In order to make effective use of waste, it has been studied to use waste plastic contained in municipal waste and industrial waste as solid fuel. Usually, such a solid fuel is produced by heat-processing waste plastic with coal in a heating furnace (for example, refer to Patent Documents 1 and 2).

  From the viewpoint of effective use of waste, it is required to produce solid fuel by increasing the use ratio of waste plastic as much as possible. On the other hand, since such a solid fuel is used as a fuel, it is naturally required to have excellent combustibility.

  In response to such demands, it has been proposed to produce waste fuel (coke) for a blast furnace by mixing waste plastic and coal and subjecting them to dry distillation in a coke oven (see, for example, Patent Document 1).

  Further, in the production of solid fuel using waste plastic, since the waste plastic is used as a raw material, it tends to be fused to the furnace wall of the heating furnace or the obtained solid fuel is agglomerated. In order to improve such a point, it has been proposed to produce a solid fuel by adding dust obtained by burning organic substances to a raw material together with waste plastic as an anti-fusing material (for example, Patent Document 2). reference).

  In addition, it has been proposed to modify low-grade coal by adding a thermoplastic resin to heated pulverized coal and coating the periphery of the pulverized coal with a thermoplastic resin (see, for example, Patent Document 3).

Japanese Patent No. 399596 JP 2008-106270 A JP-A-6-108073

  Since the manufacturing method of the solid fuel using waste plastic is normally performed on an industrial scale, it is required to manufacture the solid fuel in a high yield and a simple process. Further, the produced solid fuel is required to have good combustibility. However, in the method of Patent Document 1 described above, when the solid fuel (coke) is produced, the raw material containing the plastic is heated to a high temperature (1000 ° C. or more) and dry-distilled. And the yield of the obtained solid fuel will become low. In addition, such solid fuels are not sufficiently ignitable due to low volatile content.

  Further, in the method of Patent Document 2, since it is necessary to prepare an anti-fusing material separately, the process becomes complicated, and dust or partial combustion slag obtained by combustion is used as the anti-fusing material. Therefore, there is room for improvement in the combustibility of the obtained solid fuel. Moreover, in the method of Patent Document 3, since the molten thermoplastic resin adheres to the surface of the pulverized coal, there is a concern that the molten thermoplastic resin adheres to the inside of the apparatus. In particular, when a large amount of pulverized coal is granulated on an industrial scale, adhesion inside the apparatus can be a problem.

  The present invention has been made in view of the above circumstances, and provides a method for producing a solid fuel that can easily produce a high-yield solid fuel having good combustibility even when plastic is used as a raw material. The purpose is to provide. In addition, even if it contains a pyrolyzate of plastic, it has good flammability, and even if it uses a thermoplastic, it can sufficiently reduce the fusion to the device during production. An object is to provide a possible solid fuel.

  In order to achieve the above object, in the present invention, a solid fuel containing a powder obtained from coal and a heat-treated product obtained by heating a plastic, wherein the powder is pulverized coal obtained by pulverizing coal. And a pyrolyzate obtained by pyrolyzing the pulverized coal, the plastic contains a thermoplastic, and the heat-treated product is obtained by cooling after melting the thermoplastic. The solid fuel containing the re-solidified product, having a volatile content of 25 to 80% by mass and a fixed carbon content of 10 to 70% by mass.

  Since the solid fuel of the present invention contains a heat-treated product of plastic together with pulverized coal and / or its pyrolyzate, it is possible to effectively use waste. Moreover, since it contains a volatile matter and fixed carbon in a specific range, it has good combustibility.

  The solid fuel of the present invention preferably has a high calorific value of 20000 to 40000 kJ / kg. As a result, a calorific value substantially equal to that of coal can be obtained.

  The solid fuel of the present invention preferably has a C (carbon) content of 60 to 90 mass% and a H (hydrogen) content of 1 to 20 mass%. By containing each element in such a range, it can be set as the solid fuel which has further favorable combustibility. Such a solid fuel is particularly suitable as a fuel for burning cement.

  The solid fuel of the present invention has a first phase containing the re-solidified product and a second phase covering the outer periphery of the first phase, and the second phase adheres to the first phase. Preference is given to pulverized coal and / or pyrolysis products of pulverized coal. By having such a phase structure, the inside of a solid fuel that is normally difficult to ignite can also be combusted relatively easily. Moreover, since it has the 2nd phase so that the 1st phase with comparatively quick combustion may be covered, it becomes possible to maintain high temperature combustion over a long time.

  In the thermogravimetric analysis in which the solid fuel of the present invention is heated at a heating rate of 10 ° C./min, the difference between the weight reduction rate at 300 ° C. and the weight reduction rate at 450 ° C. is 40 to 80% on the basis of anhydrous ash. Preferably there is. Thereby, it can be set as the solid fuel which has much better combustibility.

  The solid fuel of the present invention preferably has an HGI of 10 or more. Such a solid fuel having HGI can be easily pulverized and has both good handleability and good combustibility.

  The solid fuel of the present invention is granular, and it is preferable that 50% by mass or more of the particles have a particle diameter of 1.0 mm or more and less than 30 mm. A granular solid fuel having such a particle size has both good handleability and good combustibility.

  In the solid fuel according to the present invention, 50 to 500 parts by mass of pulverized coal is mixed with 100 parts by mass of thermoplastic plastic, heated to melt at least a part of the thermoplastic plastic, and then the molten thermoplastic plastic is cooled. Thus, it is preferable to re-solidify and granulate. As a result, it is possible to obtain a solid fuel having good handleability and good combustibility while effectively utilizing waste.

  The solid fuel of the present invention is a method for producing a solid fuel having a heating step of obtaining a solid fuel by heating a mixture containing plastic and pulverized coal, wherein the plastic contains a thermoplastic, and the mixture is thermoplastic. Provided is a production method in which 50 to 500 parts by mass of pulverized coal is contained with respect to 100 parts by mass of plastic, and the yield of solid fuel with respect to the mixture in the heating step is 70% or more on a mass basis.

  Since the solid fuel obtained by the production method of the present invention is a mixture of plastic and pulverized coal at a predetermined ratio to produce a solid fuel with a high yield, the volatile content is high. Therefore, a solid fuel excellent in combustibility can be easily produced with a high yield. Moreover, since the solid fuel obtained by the said manufacturing method is a suitable range for the content of a volatile matter and pulverized coal and / or the pyrolysis product of pulverized coal, the ratio of a volatile matter and fixed carbon becomes a suitable range. It is particularly suitable as a solid fuel for cement firing that requires good combustibility.

  In the production method of the present invention, it is preferable to perform at least a part of the heating step under a negative pressure. As a result, the partial pressure of the tar component generated by the thermal decomposition of the plastic is lowered, the fusing property of the surface of the plastic melt is reduced, and the integration and agglomeration of the solids can be further reduced. By such an action, a granular solid fuel having a smaller particle diameter can be obtained.

  In the manufacturing method of this invention, it is preferable to perform the said heating process in the atmosphere whose oxygen gas concentration is 18 volume% or less. By performing thermal decomposition in such an atmosphere, the progress of oxidation is suppressed, and a solid fuel can be obtained with a higher yield.

  ADVANTAGE OF THE INVENTION According to this invention, even if it uses a plastic as a raw material, the manufacturing method of the solid fuel which can manufacture the solid fuel which has favorable combustibility easily with a high yield can be provided. In addition, even if it contains a pyrolyzate of plastic, it has good flammability, and even if it uses a thermoplastic, it can sufficiently reduce the fusion to the device during production. Possible solid fuels can be provided.

It is process drawing of the manufacturing method of the solid fuel which is one suitable embodiment of this invention. It is a block diagram of the thermal decomposition apparatus used for the manufacturing method of the solid fuel which is one suitable embodiment of this invention. It is a schematic diagram which shows the example of the stirring plate inside the rotary kiln type | mold heating furnace suitably used for the manufacturing method of the solid fuel which is preferable one Embodiment of this invention. It is a graph which shows the particle size distribution (volume basis) of the pulverized coal A used in the Example of this invention. It is a graph which shows the particle size distribution (volume basis) of the pulverized coal B used in the Example of this invention. It is a graph which shows the measurement result of the combustion rate by the DTF (Drop Tube Furnace) test of the solid fuel of Example 1A and Example 3 of this invention. It is a graph which shows the thermogravimetric analysis (TG) result of the solid fuel of Example 1A of this invention. It is a graph which shows the thermogravimetric analysis (TG) result of the solid fuel of Example 3 of this invention. It is a graph which shows the differential scanning calorimetry (DSC) result of the solid fuel of Example 2 of this invention. It is a graph which shows the differential scanning calorimetry (DSC) result of the pulverized coal A which is a raw material of Example 2 of this invention. It is a graph which shows the result of the combustion visualization test of the solid fuel of Example 2 and Example 3 of this invention. It is a scanning electron microscope (SEM) photograph (magnification: 150 times) which shows the section structure of the solid fuel obtained in Example 1A of the present invention. It is a graph which shows the relationship between the yield of a solid fuel, and the average particle diameter of a solid fuel.

  In the following, preferred embodiments of the present invention will be described with reference to the drawings as the case may be. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

  The solid fuel of this embodiment contains pulverized coal and / or a pyrolyzed product of pulverized coal, and a heat-treated product of plastic, and has a volatile content of 25 to 80% by mass and a fixed carbon content. It is 10-70 mass%. Such a solid fuel can be obtained by the above-described method for producing a solid fuel.

  The volatile content of the solid fuel of the present embodiment is preferably 45 to 65% by mass, more preferably 50 to 63% by mass. When the content of volatile matter in the solid fuel is less than 45% by mass, the yield of the obtained solid fuel is lowered, and the ignitability is deteriorated, so that sufficiently good combustibility tends to be impaired.

  By the way, when the plastic which is the raw material of the solid fuel is heated, only the flammable volatile matter is volatilized from the thermoplastic plastic which does not contain chlorine such as polyethylene. On the other hand, chlorine evaporates from plastics containing chlorine, such as vinyl chloride, together with combustible volatile components (desalting). Therefore, when the content of volatile matter in the solid fuel exceeds 65% by mass, there is no problem since the yield of volatile matter is only increased if the plastic used as the raw material is a thermoplastic plastic that does not contain chlorine. When a plastic containing chlorine is contained in the raw material, the desalting becomes insufficient as the volatile content in the solid fuel increases, and impurity components such as chlorine in the solid fuel increase. Therefore, when chlorine is contained in the thermoplastic thermoplastic material, the volatile content of the solid fuel is preferably 65% or less.

  The fixed carbon content of the solid fuel of the present embodiment is preferably 25 to 35% by mass, and more preferably 26 to 32% by mass. If the solid carbon content of the solid fuel is less than 25% by mass, the formation of an excellent high temperature field is impaired. On the other hand, when the solid carbon content of the solid fuel exceeds 35% by mass, excellent ignitability tends to be impaired.

  The ratio of fixed carbon to volatile matter (fuel ratio) is preferably 0.4 to 0.7, and more preferably 0.45 to 0.65. A solid fuel having a fuel ratio of 0.45 to 0.65 has a more excellent combustibility.

  The lower limit of the higher calorific value (air-dried basis) of the solid fuel of the present embodiment is preferably 20,000 kJ / kg, more preferably 28,000 kJ / kg, and even more preferably 30,000 kJ / kg. . If the higher calorific value of the solid fuel becomes too low, sufficiently good combustibility tends to be impaired. On the other hand, the upper limit of the higher heating value of the solid fuel is substantially 40,000 kJ / kg.

  In the present specification, the higher heating value refers to an air-drying heating value per unit weight (1 kg) measured in accordance with JIS M-8814. Moreover, the content rate of a volatile matter and fixed carbon says the content rate of an air-dry base measured based on JISM-8812.

  The solid fuel of the present embodiment is heated by mixing pulverized coal at a mass ratio of 50 to 500 parts by mass, preferably 50 to 200 parts by mass, more preferably 80 to 150 parts by mass with respect to 100 parts by mass of the thermoplastic. Then, after the thermoplastic is melted, it can be produced by a production method having a step of cooling and re-solidifying. Such a solid fuel can achieve both excellent ignitability and formation of a high temperature field at a high level, and has further excellent combustibility.

  When manufacturing the solid fuel of this embodiment, it is preferable to heat the mixture containing a thermoplastic and pulverized coal at a heating temperature of 250 to 500 ° C. At this heating temperature, some coals may or may not thermally decompose depending on the type. Thermoplastics melt at the above heating temperature, but coal does not tend to melt very much. The heating temperature is more preferably 300 to 350 ° C. However, coal hardly melts in this heating temperature region. For this reason, pulverized coal and / or pyrolysis product of pulverized coal adheres to the surface of the molten thermoplastic plastic, and a layer of pulverized coal and / or pyrolysis product of pulverized coal (the second layer described later). Phase) is formed. The presence of this second phase can reduce fusion with the apparatus and other bulk plastic melts.

  The structure of the solid fuel having the first phase and the second phase can be confirmed by observing a cross section of the solid fuel with a scanning electron microscope (SEM). The first phase may contain pulverized coal or a pyrolyzed product thereof as an accessory component in addition to the re-solidified product of the thermoplastic plastic. Moreover, the 2nd phase may contain the resolidification thing of the thermoplastic plastic as a subcomponent other than the thermal decomposition thing of pulverized coal and pulverized coal.

  In the solid fuel, when the mass ratio of the pulverized coal and / or the decomposed product of the pulverized coal becomes excessive, not only the waste cannot be effectively used but also sufficiently excellent ignitability tends to be impaired. On the other hand, when the mass ratio of the pyrolysis product of pulverized coal becomes too small, formation of a sufficiently excellent high-temperature field tends to be impaired.

  The solid fuel of the present embodiment preferably has a C (carbon) content of 60 to 90% by mass, more preferably 60 to 80% by mass, still more preferably 65 to 75% by mass; and a content of H (hydrogen). 4-9 mass%, preferably 5-8 mass%; O (oxygen) content is preferably 1-20 mass%, more preferably 2-10 mass%, still more preferably 5-10 mass%; The content is preferably 0 to 2% by mass, more preferably 0 to 1% by mass; the Cl content is preferably 1.5% by mass or less, more preferably 1.0% by mass or less. In addition, the content rate of each above-mentioned element is a value (anhydrous base) measured based on JIS M-8819.

  In the thermogravimetric analysis in which the solid fuel of the present embodiment is heated at a temperature rising rate of 10 ° C./min, the difference between the weight reduction rate at 300 ° C. and the weight reduction rate at 450 ° C. is preferably in terms of anhydrous ash. It is 40-80%, More preferably, it is 45-75%, More preferably, it is 50-65%. When the difference in weight reduction rate is less than 40%, excellent combustibility tends to be impaired, and when it exceeds 80%, formation of an excellent high temperature field tends to be impaired. In addition, the above-mentioned weight reduction amount is a value measured using a normal thermogravimetric analyzer in an air atmosphere.

  The HGI of the solid fuel of the present embodiment is preferably 10 or more, more preferably 15 or more. The higher the HGI, the easier the pulverization of the solid fuel and the easier the particle size adjustment. In addition, HGI (hard glove index, coal grindability index) can be measured using a commercially available measuring device in accordance with JIS M-8801.

  The average particle size (before pulverization) of the solid fuel of the present embodiment is preferably 2 to 15 mm, more preferably 5 to 10 mm. A solid fuel having such an average particle size before pulverization is excellent in handleability and combustibility. If the average particle size (before pulverization) of the solid fuel becomes too large, the solid fuel tends to be easily clogged at the outlet of the heating furnace for producing the solid fuel or the inlet of the facility using the solid fuel. In addition, the average particle diameter in this specification means a particle diameter (median diameter) corresponding to 50% by volume of the cumulative distribution curve. From the same viewpoint, the particle size distribution of the solid fuel (before pulverization) is preferably such that particles having a particle size of 1.0 mm or more and less than 16 mm are 70% by mass or more of the whole solid fuel, and 75% by mass or more. More preferably. The average particle size and particle size distribution of the solid fuel (before pulverization) can be measured using a commercially available particle size analyzer.

  Next, a preferred embodiment of the above-described method for producing a solid fuel will be described.

  FIG. 1 is a process diagram of a method for producing a solid fuel according to the present embodiment. The method for producing a solid fuel according to the present embodiment includes a mixing step of mixing a plastic and pulverized coal at a mass ratio of 50 to 300 parts by mass with respect to 100 parts by mass of the plastic, and heating the mixture. And a heating step for obtaining a heated product including a heat-treated product of plastic and a pyrolyzed product of pulverized coal, and a pulverizing step for crushing the heated product. Details of each step will be described below.

  In the mixing step, the plastic and pulverized coal are mixed at the above-described mass ratio. As the pulverized coal, those having a large fuel ratio (a value obtained by dividing the solid carbon content by the volatile content) such as bituminous coal and anthracite coal, that is, those having a large amount of fixed carbon are preferably used. From the viewpoint of obtaining a solid fuel that is more excellent in combustibility, pulverized coal having a high calorific value (air-dried basis) is preferably 20,000 kJ / kg or more, more preferably 25,000 kJ / kg or more. Moreover, from the viewpoint of obtaining a solid fuel excellent in ignitability, pulverized coal having a volatile content of preferably 15 to 50% by mass, more preferably 20 to 45% by mass is used.

  Further, pulverized coal having a fixed carbon content of preferably 30 to 60% by mass, more preferably 35 to 58% by mass is used. If the fixed carbon content of the pulverized coal becomes too small, the formation of an excellent high-temperature field of the obtained solid fuel tends to be impaired, and if the fixed carbon content of the pulverized coal becomes too large, it will be relatively volatile. There is a tendency that the excellent ignitability of the solid fuel obtained by reducing the content is impaired.

  As the plastic including the thermoplastic plastic, a normal waste plastic can be used. Waste plastics are usually discarded from general-purpose plastics, and most of the general-purpose plastics are thermoplastic. This waste plastic includes, for example, polyvinyl chloride, polyethylene, polypropylene, polystyrene, polyamide, and polyester as thermoplastics.

  The waste plastic may contain other plastics and may contain a small amount of waste other than plastic as impurities. Impurities are crushed to a predetermined size together with waste plastics, and even if impurities such as metal pieces and thermosetting plastics are included, they adhere to the molten block of thermoplastic or the inside Is incorporated into the solid fuel. When the clinker, which is a raw material for cement, is fired, metals and ash are added, so even if impurities are included in the solid fuel, it becomes a suitable fuel for cement firing.

  Table 1 shows an example of the composition of waste plastic used in the solid fuel production method of the present embodiment. Waste plastic A and waste plastic B in Table 1 can be suitably used as raw materials in the solid fuel production method of the present embodiment.

  From the viewpoint of obtaining a solid fuel with further excellent combustibility, the high calorific value (air-dry basis) of the entire plastic is preferably 25,000 to 40,000 kJ / kg, more preferably 30,000 to 40,000 kJ / kg. is there. Further, from the viewpoint of obtaining a solid fuel having excellent ignitability, the content of volatile components in the entire plastic is preferably 70 to 95% by mass, more preferably 80 to 90% by mass.

  In the mixing step, pulverized coal is mixed at a mass ratio of 50 to 300 parts by mass, preferably 50 to 200 parts by mass, more preferably 80 to 150 parts by mass with respect to 100 parts by mass of the thermoplastic plastic. Coal has less volatile content than thermoplastics, while thermoplastics have less fixed carbon than coal. Therefore, if the mixing ratio of the pulverized coal to the thermoplastic is too high, not only can the waste be effectively utilized, but the excellent ignitability of the obtained solid fuel tends to be impaired. On the other hand, if the mixing ratio of the pulverized coal to the thermoplastic is too low, the thermoplastic melts are fused to each other in the heating process, and the resulting heated product tends to be agglomerated and difficult to handle. . In addition, the thermoplastic resin melted on the heating furnace wall surface tends to be fused to easily damage the equipment. This is because the amount of pulverized coal adhering to the surface of the molten thermoplastic and / or the pyrolyzed product of pulverized coal is reduced, and the formation of a pulverized coal phase (second phase) having an anti-fusing function is not possible. This is enough.

  Usually, substances containing a large amount of carbon, such as pulverized coal, do not have very good wettability with molten plastic. Therefore, by mixing the pulverized coal and the plastic in the mixing step before the heating step, the separation of the pulverized coal and the thermoplastic plastic is suppressed, and the re-solidified product of the thermoplastic plastic is the main component. It is possible to obtain a solid fuel in which the first phase and the second phase mainly composed of pulverized coal and / or a pyrolyzed product of pulverized coal are well dispersed.

  FIG. 2 is a block diagram of a thermal decomposition apparatus used in the solid fuel production method of the present embodiment. The solid fuel manufacturing method of the present embodiment can use a thermal decomposition apparatus including a heating furnace that is usually used for melting waste plastic.

  As shown in FIG. 2, the waste plastic 10 that is a raw material is conveyed from a stock yard to a crusher 12 by a conveyance device 11 such as a conveyance crane, and is crushed into a predetermined size. The crushed crushed material is transferred to the heating furnace 20 by the transfer device 13. In the heating furnace 20, after pulverized coal and waste plastic are mixed, the waste plastic is heated.

  In the heating process, the thermoplastic plastic in the waste plastic is melted and solidified after the heating process to become a resolidified product. Some pulverized coals are not supposed to be thermally decomposed depending on the type of coal, and after the heating step is finished, they become a mixture of pulverized coal that is not thermally decomposed and thermally decomposed pulverized coal. Therefore, in the heating step, the mixture containing the pulverized plastic and pulverized coal is heated to obtain a granular product containing the heat-treated product of plastic including the re-solidified product and pulverized coal and / or pyrolyzed product of pulverized coal. It is done.

  When the mixture is heated in the heating furnace 20, the thermoplastic plastic is melted, and the pulverized coal and / or the thermal decomposition product of the pulverized coal is attached to the molten thermoplastic surface. Thereafter, melting of the thermoplastic plastic proceeds, and pulverized coal and / or a pyrolyzed product of pulverized coal adheres to the surface of the plastic melt. Thereafter, when cooled, a solid fuel having a structure in which the surface of the re-solidified product of the thermoplastic (first phase) is covered with pulverized coal and / or a pyrolyzed product of the pulverized coal (second phase) can be obtained. it can.

  As the heating furnace 20, a rotary heating furnace, for example, an indirect heating rotary kiln type heating furnace can be used. By using such a heating furnace, a mixture of crushed plastic and pulverized coal can be heated. The crushed plastic and pulverized coal may be mixed before being put into the heating furnace 20 or after being put into the heating furnace 20. From the viewpoint of obtaining a solid fuel that is as uniform as possible, the heating in the heating furnace 20 is preferably performed while mixing crushed plastic and pulverized coal.

  The mixture containing the crushed plastic and pulverized coal is heated by the heating furnace 20. The heating temperature in the heating furnace 20 is 250 to 500 ° C, preferably 250 to 450 ° C, more preferably 280 to 400 ° C, and particularly preferably 300 to 350 ° C. If the heating temperature is too high, the volatile content of the obtained solid fuel is reduced, the yield of the solid fuel is lowered, and the excellent combustibility of the solid fuel tends to be impaired. On the other hand, when the thermoplastic plastic contains a plastic containing chlorine, if the heating temperature is too low, the residual amount of components such as chlorine in the solid fuel tends to increase.

  The heating time for heating to the above heating temperature in the heating furnace 20 is 30 to 120 minutes, preferably 45 to 90 minutes. When the heating time is too long, the volatile content of the obtained solid fuel is decreased, and the yield of the solid fuel tends to be lowered. On the other hand, when the heating time is too short, dechlorination of the plastic becomes insufficient, and the residual amount of components such as chlorine tends to increase in the solid fuel.

  The heating in the heating furnace 20 is preferably performed under a pressure less than atmospheric pressure. This facilitates the discharge of tar components generated by the thermal decomposition of the plastic to the outside of the heating furnace. As a result, the amount of the tar component present on the surface of the thermoplastic melt is reduced, and the fusion property of the surface of the thermoplastic melt is reduced. Therefore, excessive adhesion of pulverized coal and / or pyrolysis product of pulverized coal to the surface of the thermoplastic melt is suppressed, and pulverized coal covering the thermoplastic resolidified product (first phase) and / Or it can suppress that the thickness of the thermal decomposition thing (2nd phase) of pulverized coal becomes large too much. By such an action, the particle diameter of the finally obtained solid fuel can be reduced.

  Specifically, the heating in the heating furnace 20 is preferably performed under a reduced pressure of preferably 99 kPaA or less, more preferably 98 kPaA or less. In addition, although there is no minimum in particular in the pressure in the heating furnace 20, it is preferable that it is 90 kPaA or more from a viewpoint of the pressure | voltage resistance of an installation.

  The oxygen gas concentration inside the heating furnace 20 is preferably 10 to 18% by volume, more preferably 14 to 18% by volume. If the oxygen gas concentration becomes too high, the oxidation of the thermoplastic and / or pulverized coal proceeds, and the yield of the obtained solid fuel tends to be low. On the other hand, if the oxygen gas concentration is too low, the oxidation of tar generated by thermal decomposition of the plastic is not promoted, the residual amount of tar increases, and fusion of the molten thermoplastic plastic tends to occur. .

  FIG. 3 is a schematic diagram showing an example of a stirring plate inside a rotary kiln-type heating furnace that is preferably used in the method for producing a solid fuel of the present embodiment. The stirring plate (lifter) 30 is provided so as to extend along the axial direction of the heating furnace 20. By providing such a stirring plate 30, the raw materials (plastic and pulverized coal) charged into the heating furnace 20 can be smoothly stirred and mixed. The number of the stirring plates 30 installed is appropriately set depending on the scale of the heating furnace and the like. For example, if the inner diameter of the heating furnace 20 is about 50 mm to 300 mm, it is preferable to provide two to four stirring plates 30 as shown in FIGS. 3 (a) to 3 (c). If it is about 600 mm, it is preferable to provide eight stirring plates 30 as shown in FIG.

  The stirring plate 30 is preferably attached at a pitch of about 0.3 to 3 times its height h. The height h of the stirring plate 30 is about 10% to 30% of the inner diameter of the heating furnace 20 until the plastic contained in the raw material (mixture) becomes soft and granulated with pulverized coal. Is preferred. In this way, by using the kiln having the stirring plate 30 inside, the plastic and pulverized coal charged into the heating furnace 20 are scraped up by the stirring plate 30 as the kiln rotates and heated while being mixed. It will be.

  In the method for producing a solid fuel according to the present embodiment, a thermoplastic plastic containing chlorine such as vinyl chloride (waste plastic containing vinyl chloride or the like) can be easily treated. That is, when waste plastic containing chlorine such as vinyl chloride is heated, the chlorine becomes hydrogen chloride gas and is removed (desalted) from the solid raw fuel. Thereby, a solid fuel with a sufficiently reduced chlorine content can be obtained. However, if the chlorine content in the waste plastic becomes excessive, chlorine content remains in the generated solid raw fuel, and the equipment obtained using the equipment (for example, a cement production apparatus or a power generation boiler) using the solid fuel. It can adversely affect quality (eg cement). Therefore, it is preferable that the amount of chlorine contained in the raw material plastic is small. Specifically, the chlorine content in the plastic is 30% by mass or less, preferably 10% by mass or less. In addition, from the viewpoint of effectively using waste plastic such as vinyl chloride, the chlorine content of the raw material plastic is 1% by mass or more, more preferably 2% by mass or more.

  In addition, plastics containing chlorine, such as vinyl chloride, are thermoplastic, but when dechlorination (pyrolysis) begins, they become a carbon-based solid. A particularly preferable temperature range in the heating step of the present embodiment is 300 to 350 ° C. In this temperature range, the thermoplastic plastic containing chlorine is usually solid. Therefore, in the above temperature range, the thermoplastic plastic containing chlorine is not normally melted and is not fused in the apparatus.

  On the other hand, other thermoplastics are melted and liquefied in the above temperature range (300 to 350 ° C.), and if they are put into the heating furnace 20 without adding pulverized coal, they are fused in the apparatus. . Therefore, in the present embodiment, by adding pulverized coal, the pulverized coal adheres around the molten thermoplastic plastic, even if it is a thermoplastic such as vinyl chloride, which is easier to melt than chlorine-containing plastic, It is possible to produce a solid fuel while avoiding fusion.

  Thus, in the case of producing a solid fuel using only a thermoplastic resin (polyethylene, polypropylene, polystyrene, polyamide, polyester, etc.) that does not contain chlorine, such as vinyl chloride, the effect of the solid fuel production method of the present embodiment is effective. It becomes more prominent.

  In the production method of the present embodiment, the yield of the product (solid fuel) is 70% by mass or more, preferably 75% by mass or more, and more preferably 78% by mass with respect to the entire raw material (mixture) to be charged. That's it. Thus, by maintaining the product yield high, a solid fuel having a sufficiently high volatile content and good combustibility can be obtained. In addition, the yield of a product can be adjusted by changing the heating temperature and heating time in a heating furnace.

  The heated product (solid fuel) generated in the heating process is discharged from the heating furnace 20 as a product, cooled by a cooling device (not shown), and transferred to a subsequent collection / separation device as necessary.

  On the other hand, the pyrolysis gas containing tar generated by heating the mixture in the heating furnace 20 is burned in a combustion chamber (not shown) and completely decomposed. When waste plastic containing chlorine such as vinyl chloride is used as a raw material, hydrogen chloride contained in the combustion exhaust gas is recovered by the exhaust gas cleaning device 23.

  The heated product obtained in the heating step preferably contains, as main components, a resolidified product obtained by cooling after the thermoplastic plastic melts, and pulverized coal. In addition to the main component, a small amount of thermosetting plastic that is not thermally decomposed may be contained.

  Note that, depending on the type of coal, there are some that are not thermally decomposed even when heated to 300 to 350 ° C. (a particularly preferable temperature range in the heating step of the present embodiment). Therefore, the pulverized coal contained in the main component may be a mixture of pyrolyzed coal and non-pyrolyzed coal.

  In the pulverization step, the pyrolyzate obtained in the heating step is pulverized and granulated to a desired size using a normal pulverizer. Thereby, a solid fuel having a desired particle size can be obtained.

  Prior to the pulverization step, the solid fuel obtained from the heating furnace 20 via a cooling device may be separated into one having a large particle size and one having a small particle size by means such as a vibrating sieve. In this case, those having a small particle diameter can be used as a solid fuel as they are.

  According to the method for producing a solid fuel of the present embodiment as described above, a solid having good flammability in a simple process by using plastic and pulverized coal as raw materials without performing a special pretreatment. Fuel can be obtained.

  The obtained solid fuel can be supplied to a calcining furnace of a cement production apparatus, a kiln of a rotary kiln or a kiln bottom and burned, and used as a fuel. Further, it can be supplied to a power generation boiler as an alternative fuel for pulverized coal and burned.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments. For example, in the above-described embodiment, the pulverization process is provided after the heating process, but the pyrolyzate obtained in the heating process is used as a solid fuel as it is as shown in FIG. 1 without performing the pulverization process. It is also possible.

The contents of the present invention will be described in more detail with reference to the contents of Examples and Comparative Examples, but the present invention is not limited to the following Examples.
(Examples 1-3)

  Waste plastics including polyethylene (PS), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), vinyl chloride resin and ABS resin, and commercially available pulverized coal were prepared. The results of industrial analysis and elemental analysis of the prepared waste plastic and pulverized coal are summarized in Table 2.

  In this example, the analysis of high calorific value (air-dried basis) was performed using 1013-J (device name, manufactured by Yoshida Seisakusho) in accordance with JIS M-8814. Industrial analysis (air-drying basis) was performed according to JIS M-8812. Elemental analysis (anhydrous base) was performed using MT-5 (device name, manufactured by Yanaco) in accordance with JIS M-8819. HGI (hard glove index, coal grindability index) measurement was performed in accordance with JIS M-8801. The average particle size and particle size distribution were measured using a laser diffraction particle size distribution measuring device (manufactured by Horiba, Ltd., device name: LA-920). The average particle diameter was a particle diameter (median diameter) corresponding to 50% by volume of the cumulative distribution curve.

  FIG. 4 is a graph showing the particle size distribution (volume basis) of pulverized coal A. FIG. 5 is a graph showing the particle size distribution (volume basis) of pulverized coal B.

  With respect to 100 parts by mass of the above-mentioned waste plastic, 100 parts by mass of pulverized coal A or 100 parts by mass of pulverized coal B are put into a pyrolysis apparatus equipped with a rotary kiln-type heating furnace as shown in FIG. While mixing with pulverized coal B, the temperature is raised and heated at 5 ° C./minute, and the waste plastic and pulverized coal A or pulverized coal B are mixed in a mixed gas atmosphere of nitrogen and oxygen (oxygen concentration: 5% by volume or less, Heat treatment was performed at a pressure of 98 to 101.3 kPaA).

  As a rotary kiln type heating furnace, in Example 1, it has the inner diameter shown in Table 3, a container made of heat-resistant steel SUS310S (scraping blade (stirring plate) 4 sheets (with blade height 70 mm × 4 sheets)), the container The rotary kiln type heating furnace controls the outside temperature while rotating so that the interval time between the adjacent stirring plates is 0.1 minutes, It heated so that the sample temperature in a furnace might become the heating temperature shown in Table 3. In Example 1A, 2 and 3, it implemented using the rotary kiln type | mold heating furnace similar to Example 1 which has an internal diameter shown in Table 3. Heating was performed as in Example 1.

  After the heating process was completed in the rotary kiln type furnace, the product was cooled to obtain a solid fuel containing a pyrolysis product of pulverized coal and a pyrolysis product of waste plastic. Table 3 shows the results of industrial analysis and elemental analysis of the solid fuel. Table 4 shows the analysis result of the particle size distribution of the solid fuel (before pulverization). The solid fuel analysis method and the analysis apparatus used are the same as those of the waste plastic and pulverized coal as raw materials unless otherwise specified.

In Table 3, the yield was determined by the following calculation formula (1).
Yield (mass%) = (mass of solid fuel / total mass of waste plastic and pulverized coal) × 100 (1)

  The solid fuel obtained in Example 1A and Example 3 was pulverized and sieved, and a DTF (Drop Tube Furnace) test was performed using particles having a particle diameter of 500 to 1000 μm. For comparison, the same measurement was also performed on the pulverized coal A as a raw material, which was sieved (particle diameter 60 μm). The DTF test was performed using a DTF device having an inner diameter of 90 mm and a pipe length of 2 m under a mixed gas atmosphere of air and nitrogen (oxygen concentration: 4% by volume) at a combustion temperature of 1100 ° C to 1400 ° C.

  FIG. 6 shows the combustion of particles having a particle diameter of 250 μm under conditions of an oxygen concentration of 4 vol% and a temperature of 1100 ° C. based on the burning rate data obtained by the DTF test of the solid fuels of Example 1A and Example 3. It is the graph which calculated time. From these evaluation results, it was confirmed that the solid fuel of Example 1A had a relatively high burning rate and excellent ignitability compared to pulverized coal A. In addition, it was confirmed that the burning rate comparable to that of Example 1A was obtained in Example 3.

  7 and 8 are graphs showing the thermogravimetric analysis (TG) results of the solid fuels of Example 1A and Example 3, respectively. In the thermogravimetric analysis, the solid fuel obtained in Example 1A and Example 3 was pulverized in the same manner as in the DTF test, sieved, and the particle size was in the range shown in FIGS. Went about things. For comparison, the same measurement was performed on the pulverized coal A and the pulverized coal B which are raw materials (particle diameters of 45 to 90 μm). Thermogravimetric analysis was performed by using a commercially available thermogravimetric analyzer (manufactured by Mac Science, apparatus name: MTC1000) and raising the temperature at an increase rate of 10 ° C./min in an air atmosphere. The measurement results were arranged on an anhydrous ashless basis.

  From the results shown in FIGS. 7 and 8, it was confirmed that the solid fuels (after pulverization) of Examples 1A and 3 were superior in ignitability than pulverized coal.

  FIG. 9 is a graph showing the results of differential scanning calorimetry (DSC) of the solid fuel of Example 2. FIG. 10 is a graph showing the results of differential scanning calorimetry (DSC) of pulverized coal A which is a raw material of Example 2. The calorific value of the solid fuel of Example 2 was 2.695 J / g. On the other hand, the calorific value of pulverized coal A measured under the same conditions as the measurement of the differential scanning calorific value of the solid fuel of Example 2 was 4.236 J / g. From these results, it was confirmed that the solid fuel of Example 2 has a sufficiently low self-heating value as compared with pulverized coal, and can sufficiently reduce the probability of occurrence of dust explosion.

  FIG. 11 is a graph showing the results of a combustion visualization test of solid fuels of Example 2 and Example 3. In the combustion visualization test, the solid fuel obtained in Example 2 and Example 3 was pulverized in the same manner as in the DTF test, sieved, and a commercial combustion visualization device (Japan High-tech, apparatus name: LK-1500, and Keyence, apparatus name: VB-7000) were used, and the temperature in the furnace was 1100 ° C., and air was used as the combustion gas. In addition, the same test was done also about what pulverized coal A and pulverized coal B which are raw materials were each sieved for comparison.

  As is clear from the results shown in FIG. 11, when compared with the same particle size, the solid fuel obtained in Example 2 and Example 3 may have a shorter combustion end time than pulverized coal as a raw material. confirmed. This indicates that the solid fuels of Example 2 and Example 3 have faster combustion completion and better combustibility than pulverized coal A and pulverized coal B which are raw materials.

  FIG. 12 is a scanning electron microscope (SEM) photograph (magnification: 150 times) showing the cross-sectional structure of the solid fuel obtained in Example 1A. According to this SEM photograph, the solid fuel of Example 2 is obtained by heating the thermoplastic and melting it, and then cooling the first phase 100 mainly composed of a re-solidified product and the heat of pulverized coal. It has been confirmed that the second phase 200 having a decomposition product as a main component is formed and the second phase 200 is formed so as to cover the first phase 100.

  As described above, pulverized coal and thermal decomposition products of pulverized coal adhere to the periphery of the molten thermoplastic plastic, so that the heat of the pulverized coal and pulverized coal on the surface of the re-solidified product (first phase) of the thermoplastic plastic. A layer of degradation product (second phase) was formed. Moreover, since the pulverized coal of the present example does not melt at the heating temperature (250 to 500 ° C.) in the present example, it was possible to reduce fusion inside the apparatus and excessive fusion to the plastic melt. .

  In addition, the thermogravimetric analysis (TG) curve (FIG. 7) of pulverized coal A used in Example 1, Example 1A, and Example 2 is lowered from around 360 ° C., and pulverized coal B used in Example 3 is used. The thermogravimetric analysis (TG) curve of (Figure 8) started to decrease from around 300 ° C. Since the heating temperatures in Examples 1 to 3 are 300 ° C. to 320 ° C., in the case of the solid fuels in Example 1, Example 1A, and Example 2, the thermal decomposition product of pulverized coal A is almost in the first phase. Not included. On the other hand, in the case of the solid fuel in Example 3, both the pulverized coal B and the pyrolyzed product of the pulverized coal B are included in the first phase.

  The production of the solid fuel of Example 2 was performed a plurality of times by changing the heating temperature (thermal decomposition temperature) in the heating step within a range of 250 to 340 ° C., thereby producing a plurality of solid fuels having different heating temperatures. And the relationship between the yield for each production of each solid fuel and the average particle size of the solid fuel was determined. FIG. 13 is a graph showing the relationship between the yield of solid fuel and the average particle size of the solid fuel. From the results shown in FIG. 13, a solid fuel having a small average particle diameter is obtained by producing the solid fuel so that the yield of the solid fuel is in the range of 88 to 94.8% by mass (region D1: a preferred region). It was confirmed that In addition, it is confirmed that a solid fuel having a smaller average particle diameter can be obtained by producing the solid fuel so that the yield of the solid fuel is in the range of 89 to 93% by mass (region D2: a more preferable region). It was done.

  In region D2 in FIG. 13, the desalination rate of chlorine contained in the waste plastic is 80% or more, the average particle size is small and the chlorine content is sufficiently reduced with a high desalting rate and high yield. Solid fuel could be obtained.

  20 ... heating furnace, 30 ... stirring plate (lifter), 100 ... first phase, 200 ... second phase.

Claims (11)

A solid fuel comprising a powder obtained from coal and a heat-treated product obtained by heating a plastic,
The powder contains at least one of pulverized coal obtained by pulverizing the coal and a pyrolyzed product obtained by pyrolyzing the pulverized coal,
The plastic contains a thermoplastic;
The heat-treated product contains a re-solidified product obtained by cooling after melting the thermoplastic plastic,
A solid fuel having a volatile content of 25 to 80% by mass and a fixed carbon content of 10 to 70% by mass.   The solid fuel according to claim 1, wherein the higher heating value is 20000 to 40,000 kJ / kg.   The solid fuel according to claim 1 or 2, wherein the content of C (carbon) is 60 to 90 mass% and the content of H (hydrogen) is 1 to 20 mass%. A first phase comprising the resolidified product;
A second phase covering the outer periphery of the first phase,
The solid fuel according to any one of claims 1 to 3, wherein the second phase is the pulverized coal and / or the pyrolyzate attached to the first phase. In thermogravimetric analysis, where the temperature rises at a rate of 10 ° C / min
The solid fuel according to any one of claims 1 to 4, wherein a difference between a weight reduction rate at 300 ° C and a weight reduction rate at 450 ° C is 40 to 80% based on anhydrous ash.   The solid fuel according to any one of claims 1 to 5, wherein the HGI is 10 or more.   The solid fuel according to any one of claims 1 to 6, wherein the solid fuel is in a granular form and has a particle diameter of not less than 1.0 mm and less than 30 mm with a total of 50 mass% or more of particles.   After mixing 50 to 500 parts by mass of the pulverized coal with respect to 100 parts by mass of the thermoplastic plastic and heating to melt at least a part of the thermoplastic plastic, the molten thermoplastic plastic is cooled and reused. The solid fuel according to claim 1, which is obtained by solidification and granulation. A method for producing a solid fuel comprising a heating step of heating a mixture containing plastic and pulverized coal to obtain a solid fuel,
The plastic includes a thermoplastic;
The mixture contains 50 to 500 parts by mass of the pulverized coal with respect to 100 parts by mass of the thermoplastic plastic,
The manufacturing method in which the yield of the solid fuel with respect to the mixture in the heating step is 70% or more on a mass basis.   The manufacturing method of Claim 9 which performs at least one part of the said heating process under a negative pressure.   The manufacturing method according to claim 9 or 10, wherein the heating step is performed in an atmosphere having an oxygen gas concentration of 18% by volume or less.