Fixed carbon source, metal carbide, and method for producing metal carbide

Abstract

[Problem] To provide a fixed carbon source capable of more efficiently producing an organic substance, and to provide a metal carbide and a method for producing the metal carbide. [Solution] One aspect of the present invention provides a fixed carbon source comprising a combustion residue of waste, the fixed carbon source containing silicon atoms and carbon atoms derived from the combustion residue of the waste, and the content of the silicon atoms being 10 mass% or less.

Description

Fixed carbon source, metal carbide, and method for producing metal carbide

[0001] This invention relates to a fixed carbon source, metal carbide, and a method for producing metal carbide.

[0002] For example, polyethylene and polyvinyl chloride, representative petrochemical products, are consumed in large quantities and then discarded. These waste products are a major contributor to environmental pollution. Furthermore, the mass production of petrochemical products leads to a global environmental problem: an increase in carbon dioxide in the atmosphere. To solve this problem, if waste that was previously discarded can be converted into chemical products, it will be possible to realize a resource-recycling society that does not rely on petroleum resources. From this perspective, a technology has been disclosed for producing synthesis gas from waste and then producing organic substances from that synthesis gas using a fermentation method (see Patent Document 1). Currently, there is a need for a more efficient method for producing organic substances.

[0003] Special Publication No. 2024-531893

[0004] In view of the above circumstances, the present invention aims to provide a fixed carbon source, a metal carbide, and a method for producing metal carbide that can produce organic substances more efficiently.

[0005] According to one aspect of the present invention, a fixed carbon source is provided which includes combustion residue of waste, and which contains carbon atoms derived from the combustion residue of waste and silicon atoms, wherein the silicon atom content is 10% by mass or less.

[0006] According to this embodiment, raw materials that can be used to produce organic substances more efficiently can be supplied.

[0007] Embodiments of a fixed carbon source, metal carbide, and a method for producing metal carbide will be described below. The various features shown in the embodiments below can be combined with each other. In this specification, the content of Y in X means the proportion of Y in the total X. In this specification, "waste" may include any material to be reused or processed. That is, waste is used as a concept that includes used material, unused material, virgin material, and recycled material. Furthermore, in this specification, "combustion" includes a process in which waste is reacted in the presence of oxygen, but does not necessarily mean complete combustion, and is a concept that includes incomplete combustion or partial oxidation reactions carried out under conditions where the oxygen supply or reaction conditions are limited. The combustion residue obtained by such a process may include solid residue containing fixed carbon. That is, combustion residue is used as a concept that includes residue obtained by a process including carbonization or thermal decomposition.

[0008] <Stationary Carbon Source> The stationary carbon source in this embodiment includes combustion residue from waste. This stationary carbon source contains carbon atoms derived from the combustion residue of waste and silicon atoms. Examples of silicon-based substances containing silicon atoms in the stationary carbon source include silicon oxide (silica). As will be described later, when metal carbide is produced by heating the stationary carbon source and the metal source in a heating furnace, the silicon oxide is reduced in the heating furnace as the reaction progresses to elemental silicon (Si). This elemental silicon consumes the stationary carbon source, which reacts with carbon to produce silicon carbide (SiC), thus reducing the yield of metal carbide. On the other hand, silicon oxide acts as a solvent for the melting of the metal source. Therefore, it can be expected to contribute to lowering the viscosity of the molten metal source and promoting the production of metal carbide in the heating furnace. Examples of heating furnaces include electric furnaces such as resistance furnaces, induction furnaces, and arc furnaces, gas combustion furnaces, heavy oil combustion furnaces, rotary kilns, shaft furnaces, and muffle furnaces.

[0009] For these reasons, there is a suitable range for the silicon atom content in the fixed carbon source. Specifically, the silicon atom content in the fixed carbon source is about 10% by mass or less, preferably 0.1 ppm to 10% by mass, more preferably 0.5 ppm to 5% by mass, even more preferably 1 ppm to 1% by mass, particularly preferably 5 ppm to 0.5% by mass, and most preferably 10 ppm to 0.1% by mass. In this case, the efficiency of metal carbide production can be increased while raising the yield of metal carbide.

[0010] Furthermore, the fixed carbon source may also contain at least one of phosphorus atoms and sulfur atoms. In this case, it is preferable that the phosphorus atom content in the fixed carbon source is about 1% by mass or less, and the sulfur atom content is about 5% by mass or less. By reducing the phosphorus atom content and sulfur atom content in this way, it is possible to reduce the amount of phosphine and hydrogen sulfide generated when producing organic substances, for example. As a result, the safety of organic substances for the human body can be improved. In particular, by reducing the sulfur atom content, the amount of sulfur oxides (SOx) generated can be reduced, which can prevent corrosion of components constituting the organic substance production system and adverse effects on the synthesis catalyst of organic substances.

[0011] Here, phosphorus-based substances containing phosphorus atoms in a fixed carbon source include, for example, elemental phosphorus, phosphine, phosphorus oxides, phosphorus-based plasticizers, phosphorus-based flame retardants, and phosphorus pentoxide (P ２ O ５Examples include the following. Furthermore, sulfur-based substances containing sulfur atoms in the fixed carbon source include, for example, elemental sulfur, hydrogen sulfide, sulfur oxides, factis, polysulfurized rubber, naphthenic oil, sulfur-modified chloroprene rubber, and various additives such as vulcanization accelerators containing sulfur atoms in their structure. The phosphorus atom content is preferably about 0.1% by mass or less, more preferably about 0.05% by mass or less, and even more preferably about 0.01% by mass or less. On the other hand, the sulfur atom content is preferably about 0.5% by mass or less, more preferably about 0.05% by mass or less, and even more preferably about 0.005% by mass or less. By setting the phosphorus atom content and sulfur atom content within these ranges, the above effects can be further improved.

[0012] From a safety standpoint, it is preferable that the phosphorus and sulfur atom content in the fixed carbon source be as low as possible. However, by leaving a small amount of phosphorus (phosphorus-based substances) and sulfur (sulfur-based substances) in the fixed carbon source, a small amount of, for example, phosphine and hydrogen sulfide will remain in the acetylene and monomer compounds obtained using the fixed carbon source. For example, the phosphine and hydrogen sulfide contained in the acetylene will react with oxygen, consuming the oxygen, thus suppressing the mixing of acetylene and oxygen, and thus the safety of the acetylene is less likely to be compromised. In addition, because the oxygen content in the acetylene is low, a decrease in the yield of the monomer compound obtained from acetylene, and consequently the yield of the polymer, can be prevented or suppressed. Furthermore, acetylene containing phosphine and hydrogen sulfide will have a slight odor, so even if acetylene leaks, it can be detected, thus providing high safety from this standpoint as well.

[0013] In this case, the phosphorus atom content in the fixed carbon source is preferably about 0.1 ppm (0.00001 mass%) or more, more preferably about 1 ppm (0.0001 mass%) or more, and even more preferably about 10 ppm (0.001 mass%) or more. The phosphorus atom content can be, for example, 0.1 ppm to 1 mass% or less. On the other hand, the sulfur atom content in the fixed carbon source is preferably about 0.1 ppm (0.00001 mass%) or more, more preferably about 1 ppm (0.0001 mass%) or more, and even more preferably about 10 ppm (0.001 mass%) or more. The sulfur atom content can be, for example, 0.1 ppm to 5 mass% or less. By setting the phosphorus atom content and sulfur atom content within these ranges, the above effects can be further improved.

[0014] Furthermore, the nitrogen atom content in the fixed carbon source is preferably about 20% by mass or less, more preferably about 10% by mass or less, and even more preferably about 5% by mass or less. Reducing the nitrogen atom content also reduces the amount of nitrogen oxides generated, which can prevent corrosion of components constituting the organic substance production system and adverse effects on the organic substance synthesis catalyst. The silicon atom content in the fixed carbon source can be measured using ICP emission spectrometry. In addition, the phosphorus, sulfur, and nitrogen atom content in the fixed carbon source can be measured according to JIS M 8813:2004. Furthermore, the content of various atoms in the fixed carbon source can be determined, for example, by selecting the type of waste, setting its combination and mixing ratio, and other factors such as silicon dioxide (SiO₂). ２ ), phosphorus-based plasticizers, phosphorus-based flame retardants, phosphorus pentoxide (P ２ O ５ ), can be adjusted by adding additives containing silicon atoms in the structure, additives containing sulfur atoms in the structure, and additives containing nitrogen atoms in the structure. In other words, the various atoms may be present in the waste or added later.

[0015] Further, the fixed carbon source preferably contains no ash or, if it contains ash, the content thereof is preferably low. Here, examples of the ash include silicon oxide (SiO ２ ), and in addition, for example, rare earth oxides (R ２ O ３ ), calcium oxide (CaO), magnesium oxide (MgO), sulfur oxides (SO ３ ), and the like. These ash components, for example, when producing acetylene, are reduced in the heating furnace, thereby reducing the production efficiency and quality of acetylene. Specifically, when magnesium oxide is reduced in the heating furnace, it becomes elemental magnesium, which volatilizes and rises above the heating furnace. When it contacts air, it is oxidized back to magnesium oxide, descends below the heating furnace, and is reduced again. To repeat such oxidation and reduction, power is wasted uselessly. Also, when magnesium oxide is reduced, carbon is wasted.

[0016] Similarly, silicon oxide also wastes power by the volatilization and oxidation of elemental silicon generated by reduction. In addition, the silicon carbide formed as described above is a crystal called so-called carborundum, which has a high melting point and is extremely hard. Therefore, when silicon carbide accumulates in the heating furnace, ultimately the heating furnace may become blocked and operation may become impossible. To avoid the above problems, the content of the ash in the fixed carbon source in terms of the total ash is preferably about 30% by mass or less, more preferably about 20% by mass or less, and even more preferably about 7% by mass or less. The content of the ash in the fixed carbon source can be measured in accordance with JIS M 8812:2006. The content of the ash in the fixed carbon source can be adjusted, for example, by selecting the type of waste, setting its combination and mixing ratio, and using additives containing any one or more of silicon atoms, rare earth atoms, calcium atoms, magnesium atoms, and sulfur atoms in the structure. That is, the ash may be contained in the waste or may be added later.

[0017] As mentioned above, the fixed carbon source includes the combustion residue of waste. After pre-treatment such as crushing and drying, the waste is subjected to a carbonization treatment for about one hour at a temperature of approximately 400°C to 1000°C, under a low-oxygen atmosphere (oxygen concentration of approximately 10% by volume or less), or under an inert gas atmosphere such as nitrogen or argon, using a rotary kiln, fluidized bed furnace, or high-temperature vacuum atmosphere furnace, thereby obtaining charred material corresponding to the combustion residue in this specification. In such treatment under low-oxygen conditions, some components in the waste undergo an oxidation reaction, while a considerable portion of the carbon component remains unoxidized as a solid. Here, it is preferable that the waste includes at least one of waste plastics, waste rubber, and waste carbon fibers. By utilizing such waste, which is a major cause of environmental pollution, it becomes easier to realize a resource-recycling society that does not rely on petroleum resources.

[0018] The waste plastic is preferably at least one selected from the group consisting of, for example, polyethylene, polystyrene, polypropylene, polyvinyl chloride, phenolic resin, polyacetal, polycarbonate, polyamide, modified polyphenylene ether, polyetherether ketone, polyethersulfone, polyetherimide, polyphenylene sulfide, polysulfone, liquid crystal polymer, polyethylene terephthalate, and polybutylene terephthalate.

[0019] The waste rubber is preferably at least one selected from the group consisting of, for example, natural rubber, styrene-butadiene rubber, butadiene rubber, isoprene rubber, butyl rubber, acrylonitrile-butadiene rubber, chloroprene rubber, ethylene-propylene rubber, acrylic rubber, fluororubber, silicone rubber, urethane rubber, and epichlorohydrin rubber. The waste may further include at least one of glass and silica sand.

[0020] Furthermore, if the combustion residue contains metal, it is preferable to separate the metal from the combustion residue by crushing, sieving, or magnetic force. Also, if polyvinyl chloride, chloroprene rubber, etc., are used as waste, the combustion residue may contain unwanted components such as chlorine. In this case, it is preferable to remove the chlorine from the combustion residue by washing the waste with water before and / or after the carbonization treatment. In addition, if necessary, the powdered combustion residue may be granulated to a certain size before use.

[0021] The fixed carbon source is preferably such that the crushing strength of a sample molded to a size of 35 mm x 35 mm x 10 mm is 10 kgf or more, more preferably 20 kgf or more, even more preferably 30 kgf or more, and particularly preferably 40 kgf or more, as measured according to JIS Z 8841:1993. The upper limit of the crushing strength of the sample is not particularly limited, but is approximately 60 kgf. The crushing strength of the sample can be, for example, between 10 kgf and 60 kgf. This makes it easier to handle the fixed carbon source when producing organic substances such as acetylene.

[0022] Furthermore, the fixed carbon source preferably has a volatile content of 5% by mass or less, more preferably around 4% by mass or less, and even more preferably around 3% by mass or less, as measured according to JIS M 8812:2006. The lower limit of the volatile content of the fixed carbon source is not particularly limited, but is approximately 0.01% by mass. The volatile content of the fixed carbon source can be, for example, 0.01% by mass or more and 5% by mass or less. This effectively prevents the fixed carbon source from burning during storage, etc.

[0023] The fixed carbon source preferably contains 70% or more carbon atoms derived from the combustion residue of waste, more preferably 80% or more, even more preferably 90% or more, particularly preferably 95% or more, and may be substantially 100% or more. By using a fixed carbon source with a high content of carbon atoms derived from the combustion residue of waste in this way, it is easier to produce high-purity organic substances (e.g., acetylene). Furthermore, by setting the content of carbon atoms derived from the combustion residue of waste in the fixed carbon source within the above range, it is easier to realize a resource-recycling society that does not rely on petroleum resources.

[0024] <Metal Carbide> The metal carbide of this embodiment contains carbon atoms derived from the fixed carbon source described above. In this case, the content of phosphorus atoms (phosphorus-based substances) and sulfur atoms (sulfur-based substances) in the metal carbide can be reduced. Therefore, the same effects as those described for fixed carbon sources can be obtained. The metal carbide has the chemical formula: MC or MC ２ This compound is represented as (where M is a metal atom) and is used, for example, as a convenient source of acetylene. Furthermore, industrially important compounds that are raw materials for various plastics (e.g., 2-chloro-1,3-butadiene: chloroprene monomer, etc.) can be obtained from acetylene.

[0025] Metal carbides are preferably used to produce acetylene. This is because industrially important compounds (organic substances) that serve as raw materials for various plastics can be produced from acetylene. For example, ethylene can be produced by hydrogenating acetylene, acrylonitrile by reacting acetylene with hydrogen cyanide, vinyl chloride by reacting acetylene with hydrogen chloride, acrylic acid by reacting acetylene with carbon monoxide and water, monovinylacetylene by dimerizing acetylene, vinyl acetate by reacting acetylene with acetic acid, and acetaldehyde by reacting acetylene with water. Furthermore, acrylic acid can be reacted with alcohol to produce acrylic acid esters. Acetylene black can also be produced by thermal decomposition of acetylene. Note that hydrogen sulfide (SH) in acetylene... ２ ), phosphine (PH ３ ), arsine (hydrogen arsenide: AsH ３ ), ammonia (NH ３ By reducing the content of impurity gases such as ), the quality of acetylene can be improved.

[0026] Metal carbides are also preferably used to produce calcium cyanamide. Calcium cyanamide mainly consists of calcium cyanamide and also contains calcium oxide, etc. Calcium cyanamide exhibits pesticide effects (insecticidal, herbicidal, and fungicidal effects), then decomposes into fertilizer components in the soil, leaving no residue and making it safe to use. Furthermore, calcium cyanamide is not easily leached from the soil and exhibits a slow-release effect, allowing for a reduction in the frequency and amount of fertilization. Using calcium cyanamide can also correct soil acidity and promote the decomposition of organic matter, making it easier to create soil suitable for cultivation. Such calcium cyanamide can be produced, for example, by absorbing nitrogen into the above-mentioned metal carbides at high temperatures.

[0027] The metal carbide reacts with pure water to generate acetylene, and the sulfur atom content in the metal carbide is preferably about 100 ppm or less, more preferably about 90 ppm or less, even more preferably about 80 ppm or less, particularly preferably about 50 ppm or less, and may be 0 ppm. The metal carbide reacts with pure water to generate acetylene, and the phosphorus atom content in the metal carbide is preferably 1 ppm to 320 ppm, more preferably about 5 ppm to 250 ppm, even more preferably about 10 ppm to 200 ppm, and particularly preferably about 20 ppm to 180 ppm.

[0028] <Method for Manufacturing Metal Carbide> The metal carbide described above can be manufactured, for example, by the following method for manufacturing metal carbide. The method for manufacturing metal carbide in this embodiment includes a preparation step of preparing a fixed carbon source containing combustion residue of waste and a metal source, and a heating step of heating the fixed carbon source and the metal source in a heating furnace. Each step will be described below. The fixed carbon source containing combustion residue of waste can be obtained as a carbide by the carbonization treatment of waste as described above, and its properties (crushing strength, volatile content, etc.), as well as the silicon atom content, can be easily adjusted to a desired range.

[0029] <<Preparation Process>> First, a fixed carbon source containing combustion residue of waste and a metal source are prepared. In particular, using a fixed carbon source capable of forming a sample with the crushing strength described above can effectively prevent collapse during preparation and in the heating furnace. On the other hand, examples of metal sources include alkaline earth metal oxides, alkaline earth metal carbonates, alkaline earth metal hydroxides, alkaline earth metal sulfates, alkaline earth metal chlorides, etc. These metal sources may be used individually or in combination of two or more. The metal source preferably contains an alkaline earth metal oxide or carbonate (e.g., calcium oxide, barium oxide, or barium carbonate), and more preferably contains calcium oxide. Calcium oxide (CaO) is, for example, calcium carbonate (CaCO3). ３It is an unstable substance obtained by thermal decomposition of ) at approximately 900°C. For this reason, calcium oxide is suitable as a metal source due to its high reactivity. Suitable metal carbides include calcium carbide, barium carbide, and magnesium carbide.

[0030] <<Heating Process>> Next, the mixture of the fixed carbon source and the metal source is placed in a heating furnace and heated. This causes the fixed carbon source and the metal source to react to obtain metal carbide. The heating temperature is not particularly limited, but is preferably between 1700°C and 2200°C, and more preferably between 1900°C and 2100°C. The heating time is also not particularly limited, but when the above heating temperatures are used, it is preferably between 2 minutes and 3 hours, and more preferably between 30 minutes and 1.5 hours. By heating under these conditions, the reaction between the fixed carbon source and the metal source can be sufficiently carried out.

[0031] The heating atmosphere is preferably an inert gas atmosphere such as an argon gas atmosphere. This prevents the rapid combustion (consumption) of the fixed carbon source and the unwanted combustion of carbon monoxide and hydrogen generated during the reaction between the fixed carbon source and the metal source. The amount of the fixed carbon source is preferably 30 to 400 parts by mass, more preferably 50 to 300 parts by mass, and even more preferably 70 to 200 parts by mass, per 100 parts by mass of the metal source. By reacting in such a ratio, the yield of metal carbide can be sufficiently increased. The fixed carbon source and the metal source are preferably in particulate form. This increases the contact area between the fixed carbon source and the metal source, thereby improving their reaction efficiency.

[0032] The average particle diameter of the fixed carbon source is not particularly limited, but is preferably about 8 mm to 50 mm, more preferably about 8 mm to 30 mm, and even more preferably about 8 mm to 10 mm. Similarly, the average particle diameter of the metal source is not particularly limited, but is preferably about 8 mm to 50 mm, more preferably about 8 mm to 30 mm, and even more preferably about 8 mm to 10 mm. In this specification, the average particle diameter refers to the particle diameter (D50) when the cumulative value in the volume-based cumulative particle size distribution obtained by laser diffraction scattering reaches 50%. The laser diffraction scattering method is measured in accordance with the method described in JIS Z 8825:2013 "Particle size analysis - Laser diffraction and scattering method".

[0033] Prior to the main heating described above, preheating may be performed by heating the mixture at a temperature lower than the main heating temperature. By performing such preheating, the amount of fixed carbon source consumed during the main heating can be reduced, and the yield of metal carbide can be further increased. Examples of fuel for preheating include the gas emitted during the main heating (a mixture of carbon monoxide and hydrogen). By using this gas as fuel for preheating, energy can be effectively utilized while effectively preventing air pollution.

[0034] Also, in this heating step, the gas containing at least carbon monoxide and hydrogen generated in the heating furnace may be recovered. That is, the method for producing metal carbide may further have a recovery step of recovering the gas containing carbon monoxide and hydrogen. The recovered carbon monoxide and hydrogen may be used, for example, as an energy source when converting calcium carbonate to calcium oxide or as an energy source when converting metal carbide to acetylene, and they may be converted to carbon compounds using these. In the latter case, the method for producing metal carbide may further have a reaction step of reacting at least carbon monoxide and hydrogen to obtain a carbon compound. Thereby, effective utilization of the gas generated in the production process of metal carbide can be achieved. Examples of this carbon compound include acrylic acid, olefins (jet fuel), acetylene black, and the like.

[0035] Further, it may be provided in each of the aspects described below.

[0036] (1) A fixed carbon source containing combustion residues of waste, containing carbon atoms derived from the combustion residues of the waste and silicon atoms, and having a silicon atom content of 10% by mass or less.

[0037] (2) The fixed carbon source according to (1) above, having a silicon atom content of 0.1 ppm or more.

[0038] (3) The fixed carbon source according to (1) or (2) above, further containing at least one of phosphorus atoms and sulfur atoms, having a phosphorus atom content of 1% by mass or less and a sulfur atom content of 5% by mass or less.

[0039] (4) In the fixed carbon source according to any one of (1) to (3) above, the crushing strength measured according to JIS Z 8841:1993 for a sample obtained by shaping the fixed carbon source to a size of 35 mm × 35 mm × 10 mm is 10 kgf or more.

[0040] (5) In the fixed carbon source according to any one of (1) to (4) above, the volatile content measured according to JIS M 8812:2006 is 5% by mass or less.

[0041] (6) A fixed carbon source according to any one of (1) to (5) above, wherein the carbon content is 70% by mass or more.

[0042] (7) A metal carbide containing carbon atoms derived from any one of the fixed carbon sources described in (1) to (6) above.

[0043] (8) A metal carbide used to produce acetylene in the metal carbide described in (7) above.

[0044] (9) A metal carbide used to produce calcium cyanamide, as described in (7) above.

[0045] (10) A metal carbide according to any one of (7) to (9) above, wherein the metal carbide reacts with pure water to generate acetylene, and the sulfur atom content in the metal carbide is 100 ppm or less.

[0046] (11) A metal carbide according to any one of (7) to (10) above, wherein the metal carbide reacts with pure water to generate acetylene, and the content of phosphorus atoms in the metal carbide is 1 ppm or more and 320 ppm or less.

[0047] (12) A method for producing metal carbide, comprising a preparation step of preparing a fixed carbon source containing combustion residue of waste and a metal source, and a heating step of heating the fixed carbon source and the metal source in a heating furnace.

[0048] (13) A method for producing metal carbide as described in (12) above, wherein the metal source comprises an oxide or carbonate of an alkaline earth metal.

[0049] (14) A method for producing a metal carbide as described in (12) or (13) above, wherein the content of phosphorus atoms in the fixed carbon source is 0.1 ppm or more.

[0050] (15) A method for producing a metal carbide according to any one of (12) to (14) above, wherein the content of sulfur atoms in the fixed carbon source is 0.1 ppm or more.

[0051] (16) A method for producing a metal carbide according to any one of (12) to (15) above, further comprising a recovery step of recovering a gas containing at least one of carbon monoxide and hydrogen.

[0052] (17) A method for producing a metal carbide as described in (16) above, further comprising a reaction step of reacting at least the carbon monoxide with the hydrogen to obtain a carbon compound. Of course, this is not limited to this method.

[0053] Finally, while various embodiments relating to this disclosure have been described, these are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0054] The fixed carbon source, metal carbide, and method for producing metal carbide will be described in more detail below using the following examples and comparative examples, but these are not limited to the following examples.

[0055] 1. Preparation of raw materials <Steady carbon sources> <<Steady carbon sources A-L and Q-R>> First, 1 kg of waste containing at least one of waste plastic and waste rubber (see Tables 1 and 2 below) was crushed and then pre-treated by drying. After that, carbonization treatment was carried out at approximately 1000°C under a nitrogen atmosphere for 1 hour using a high-temperature vacuum atmosphere furnace (Hirochiku Co., Ltd., "CVF-2030"). This yielded sitid carbon sources A-L and Q-R containing combustion residue of the waste. The sitid carbon sources A-L and Q-R were then crushed and separated using a sieve so that the average particle size was approximately 10 mm.

[0056] <<Steady Carbon Sources M-P>> First, 1 kg of waste plastic (see Table 2 below) was melted and poured into a 10 cm x 10 cm x 10 cm mold, followed by cooling and drying as a pretreatment. Then, sitting carbon sources M-P were obtained by carbonization treatment similar to that of sitting carbon sources A-L and Q-R. Sifty carbon sources M-P were crushed and separated using a sieve so that the average particle size was approximately 10 mm. <Calcium Source (Metal Source)> Calcium oxide (manufactured by Denka Co., Ltd.) with an average particle size of 10 mm was prepared.

[0057] 2. Production of Calcium Carbide (Metal Carbide) (Example 1) First, a mixture was obtained by mixing 100 parts by mass of a fixed carbon source A with 195 parts by mass of calcium oxide as a calcium source. Next, this mixture was placed in a high-temperature vacuum atmosphere furnace (Hirochiku Co., Ltd., "CVF-2030") and heated at 2000°C for 30 minutes while flowing argon at a rate of 7 L / hr. Calcium carbide was obtained as a result.

[0058] (Examples 2-16) Calcium carbide was obtained in the same manner as in Example 1, except that fixed carbon sources B-P were used instead of fixed carbon source A. (Comparative Examples 1-2) Calcium carbide was obtained in the same manner as in Example 1, except that fixed carbon sources Q-R were used instead of fixed carbon source A.

[0059] 3. Measurement and Evaluation 3-1. Measurement of silicon atom content in fixed carbon source Approximately 0.1 g of fixed carbon source is mixed with 6 mL of 20% HCl and 20% HNO ３ Two mL of [a specific solution] was added to decompose the sample. The sample was then heated to 220°C for 35 minutes using a microwave decomposition system. After cooling, the sample was diluted to 25 mL with ultrapure water. Calibration curves were then created using an ICP emission spectrometer (Agilent 5800 VDV ICP-OES) from 1000 mg / L and 10000 mg / L Si single-element standard solutions. Similarly, elemental analysis of the sample decomposition products was performed, and the silicon atom content in the sample decomposition products (fixed carbon source) was determined from the calibration curve.

[0060] 3-2. Measurement of phosphorus and sulfur atom content in fixed carbon sources The phosphorus and sulfur atom content in fixed carbon sources was measured in accordance with JIS M 8813:2004. 3-3. Measurement of carbon atom content in fixed carbon sources The carbon atom content in fixed carbon sources was measured in accordance with JIS M 8812:2006.

[0061] 3-4. Measurement of crushing strength A sample was obtained by molding a fixed carbon source to a size of 35 mm × 35 mm × 10 mm. The crushing strength of this sample was measured according to JIS Z 8841:1993. 3-5. Measurement of volatile matter The volatile matter of the fixed carbon source was measured according to JIS M 8812:2006.

[0062] 3-6. Yield of Calcium Carbide The yield of calcium carbide was determined according to the following formula 1. Formula 1: Yield (%) = Weight of sample after reaction (g) × Purity (%) / Theoretical yield (g) First, the theoretical yield was calculated by subtracting the weight corresponding to impurities in calcium oxide, water, volatile matter, and ash from the weight of the sample before the reaction, and then calculating the weight that actually participates in the reaction: CaO + 3C ⇒ CaC ２ The purity was calculated using the formula +CO. Furthermore, the purity was determined from the amount of acetylene generated according to the following formula 2. One mole of calcium carbide obtained in each example and comparative example was mixed with 2.5 moles of distilled water and then heated at 120°C. This generated acetylene, which was collected in a container, and the volume (L) of generated acetylene under standard conditions was measured. Formula 2: Purity (%) = Volume of generated acetylene (L) / Theoretical amount of acetylene generated (L) × 100

[0063] 3-7. Measurement of Oxygen, Phosphine, and Hydrogen Sulfide Content in Acetylene The oxygen content in the acetylene recovered in "3-6" above was measured by gas chromatography-mass spectrometry using an Agilent 7820A GC system (manufactured by Agilent Technologies, Inc.) equipped with a TCD detector. The content (volume fraction) of phosphine and hydrogen sulfide was measured using a UV-1800 (manufactured by Shimadzu Corporation) according to the absorbance spectrophotometric method described in JIS K 1901:2003 5.4.1.

[0064] These results are shown in Tables 1 and 2 below.

[0065]

[0066] The abbreviations in Tables 1 and 2 are as follows: PP: Polypropylene PE: Polyethylene PS: Polystyrene CR: Chloroprene rubber vulcanized product NBR: Nitrile rubber vulcanized product SiO ２ -rich: Waste containing a large amount of silicon dioxide P-rich: Waste containing a large amount of phosphorus atoms SM-CR: Sulfur-modified chloroprene rubber vulcanized product

[0067] As shown in Tables 1 and 2, it was found that using fixed carbon sources A to P with appropriate silicon atom content resulted in higher yields of calcium carbide and acetylene.

Claims

1. A fixed carbon source containing combustion residue of waste, wherein the fixed carbon source contains carbon atoms derived from the combustion residue of the waste and silicon atoms, and the content of silicon atoms is 10% by mass or less.

2. A fixed carbon source according to claim 1, wherein the silicon atom content is 0.1 ppm or more.

3. A fixed carbon source according to claim 1, further comprising at least one of a phosphorus atom and a sulfur atom, wherein the phosphorus atom content is 1% by mass or less and the sulfur atom content is 5% by mass or less.

4. A fixed carbon source according to claim 1, wherein the crush strength of a sample of the fixed carbon source molded to a size of 35 mm × 35 mm × 10 mm is 10 kgf or more, as measured according to JIS Z 8841:1993.

5. A fixed carbon source according to claim 1, wherein the volatile content measured in accordance with JIS M 8812:2006 is 5% by mass or less.

6. A fixed carbon source according to claim 1, wherein the carbon content is 70% by mass or more.

7. A metal carbide containing carbon atoms derived from a fixed carbon source according to any one of claims 1 to 6.

8. A metal carbide according to claim 7, which is used to produce acetylene.

9. A metal carbide according to claim 7, which is used to produce calcium cyanamide.

10. A metal carbide according to claim 7, wherein the metal carbide reacts with pure water to generate acetylene, and the sulfur atom content in the metal carbide is 100 ppm or less.

11. A metal carbide according to claim 7, wherein the metal carbide reacts with pure water to generate acetylene, and the content of phosphorus atoms in the metal carbide is 1 ppm or more and 320 ppm or less.

12. A method for producing metal carbide, comprising: a preparation step of preparing a fixed carbon source containing combustion residue of waste and a metal source; and a heating step of heating the fixed carbon source and the metal source in a heating furnace, the method for producing calcium carbide.

13. A method for producing a metal carbide according to claim 12, wherein the metal source comprises an oxide or carbonate of an alkaline earth metal.

14. A method for producing a metal carbide according to claim 12 or claim 13, wherein the content of phosphorus atoms in the fixed carbon source is 0.1 ppm or more.

15. A method for producing a metal carbide according to claim 12 or claim 13, wherein the content of sulfur atoms in the fixed carbon source is 0.1 ppm or more.

16. A method for producing a metal carbide according to claim 12 or claim 13, further comprising a recovery step of recovering a gas containing at least one of carbon monoxide and hydrogen.

17. A method for producing a metal carbide according to claim 16, further comprising a reaction step of reacting at least the carbon monoxide with the hydrogen to obtain a carbon compound.

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