Method for reducing molecular weight of organic substances

Abstract

Provided is a method that can more efficiently reduce the molecular weight of and gasify organic substances. The present invention is a method for reducing the molecular weight of organic substances, the method comprising: a step for mixing water vapor with a carbon monoxide-containing gas wherein the number of molecules of the former exceeds the number of carbon monoxide molecules, and bringing about a shift reaction to obtain a mixed gas that contains hydrogen and carbon dioxide produced by the shift reaction and the excess water vapor not consumed by the shift reaction; and a step for introducing an organic substance and the mixed gas into a fluidized bed in which a powder material is being fluidized, and recovering a lower molecular weight product produced by a chemical reaction between the organic substance and the mixed gas. The present invention is characterized in that superheated water vapor is additionally introduced into the fluidized bed.

Description

Methods for reducing the molecular weight of organic substances

[0001] The present invention relates to a method for reducing the molecular weight of organic substances, and is not particularly limited, but concerns a method for modifying organic polymers such as plastics, rubber, and elastomers to convert them into low-molecular-weight products, and utilizing the obtained low-molecular-weight products as gaseous fuels, etc.

[0002] Many industrial wastes containing organic polymers, such as waste plastics, oily sludge, and waste rubber, are currently incinerated because so-called chemical recycling technologies, which convert them into other substances through chemical treatment, have not yet been established. However, incinerating organic polymers produces CO2, which has a high environmental impact. ２ These issues arise, and the high heat generated can lead to thermal damage to incinerators. Therefore, there is a need to establish chemical recycling technologies for organic polymers. In particular, technologies for converting organic polymers into low-molecular-weight products such as gaseous and liquid fuels have been studied extensively, mainly focusing on waste plastics.

[0003] For example, the prior art disclosed in Patent Document 1 is a method for promoting the thermal decomposition and hydrodecomposition of organic substances by reacting COG (hereinafter sometimes referred to as "COG"), which is generated in the carbonization process using a coke oven and has a hydrogen concentration of 60 vol% or more and a temperature of 600°C or higher, with organic substances such as waste plastics. By reacting COG containing a high concentration of hydrogen with organic substances, the hydrodecomposition of organic substances is promoted.

[0004] Furthermore, the prior art disclosed in Patent Document 2 is a method for reducing the molecular weight of organic substances by adding excess water vapor to exhaust gas containing carbon monoxide to carry out a shift reaction, thereby creating a mixed gas containing hydrogen and carbon dioxide produced in the shift reaction, and excess water vapor not consumed in the shift reaction, and then contacting this mixed gas with an organic substance to modify the organic substance and reduce its molecular weight. Here, "shift reaction" refers to the chemical reaction represented by the following chemical formula (1). In the shift reaction, carbon monoxide and water vapor react to produce hydrogen and carbon dioxide. This makes it possible to increase the concentration of hydrogen in the mixed gas. CO + H２ O→H ２ +CO ２ ... (1)

[0005] Furthermore, Patent Document 3 discloses a method for reducing the molecular weight of organic substances, which is an advanced version of the prior art disclosed in Patent Document 2. This method involves contacting a mixed gas with an organic substance in a fluidized bed containing granular material that includes at least one element selected from Fe, Ni, and Cr. This method prevents the adhesion of organic substances that is a problem in flow-type fixed-bed reactors by using a fluidized bed reactor as the reforming reactor. In addition, since the granular material also functions as a catalyst, the reaction to reduce the molecular weight of organic substances proceeds more efficiently.

[0006] Japanese Patent Publication No. 2007-224206, Japanese Patent Publication No. 2012-188641, Japanese Patent Publication No. 2014-37524

[0007] The method disclosed in Patent Document 3 for reducing the molecular size of organic substances using a mixed gas inside a fluidized bed is an excellent method in terms of processing efficiency and cost. However, the prior art disclosed in Patent Document 3 had the following unresolved problems.

[0008] The inventors compared the degree of molecular weight reduction reaction between using converter dust generated at a steel mill and silica sand as the granular material for the molecular weight reduction method for organic substances disclosed in Patent Document 3. Since converter dust contains Fe, Ni, and Cr, which have catalytic functions, and silica sand does not, it was expected that the molecular weight reduction reaction would proceed more easily with converter dust than with silica sand. However, the actual investigation revealed that the degree of molecular weight reduction reaction did not differ much regardless of the type of granular material. This is presumed to be because the undecomposed organic substance components adhered to the surface of the converter dust, hindering contact between the organic substance and the converter dust, and as a result, the catalytic functions of Fe, Ni, and Cr contained in the converter dust did not work effectively.

[0009] Furthermore, although not entirely clear from the comparative studies mentioned above, if undecomposed organic substances adhere to the surface of the granular material, not only will its catalytic function be impaired, but the granular material may aggregate, making it difficult to maintain a fluid state. When the granular material loses its fluidity, its functions of mixing reactants and conducting heat are impaired, hindering the progress of the chemical reaction. Aggregation of granular material is particularly likely to occur when the low-molecular-weight products generated by the demolecularization of organic substances include high-viscosity tar.

[0010] Therefore, the object of the present invention is to provide a method for reducing the molecular weight of organic substances, in which excess water vapor is added to a gas containing carbon monoxide to generate hydrogen gas and carbon dioxide gas by a shift reaction, a mixed gas containing the generated hydrogen gas and carbon dioxide gas and excess water vapor not consumed in the shift reaction is obtained, the mixed gas and organic substances are introduced into a fluidized bed in which powders and granules are flowing, and low molecular weight products generated by a chemical reaction between the organic substances and the mixed gas are recovered, thereby preventing undecomposed organic substance components from adhering to the surface of the powders and granules inside the fluidized bed reactor, and enabling efficient reduction of the molecular weight and gasification of organic substances.

[0011] As a result of their extensive research to solve the above problems, the inventors discovered that by directly introducing superheated steam into the fluidized bed in which the powder is flowing, in addition to the mixed gas containing excess steam not consumed in the shift reaction, the demolition reaction of organic substances in the fluidized bed is promoted, and more efficient gasification can be achieved. Here, "superheated steam" refers to steam heated to a temperature higher than the boiling point of water. Superheated steam has a specific heat of about twice that of air and is steam with extremely high hydrolysis capacity. By directly introducing superheated steam into the fluidized bed, the decomposition of organic substances is promoted, and it is possible to prevent undecomposed organic substances from adhering to the powder.

[0012] The inventors further discovered that when the organic substance of the material to be treated includes rubber or elastomer, the hydrocracking reaction is further accelerated, enabling the efficient production of high-calorie, low-molecular-weight products, and is also effective in suppressing tar generation, thus completing the present invention.

[0013] The gist of this invention is as follows:

[0014] [1] A method for reducing the molecular weight of an organic substance, comprising the steps of: mixing a gas containing carbon monoxide with water vapor in a number exceeding the number of carbon monoxide molecules to cause a shift reaction, thereby obtaining a mixed gas containing hydrogen and carbon dioxide produced by the shift reaction, and excess water vapor not consumed by the shift reaction; and introducing an organic substance and the mixed gas into a fluidized bed in which granular material is flowing, and recovering low molecular weight products generated by a chemical reaction between the organic substance and the mixed gas, wherein superheated water vapor is further introduced into the fluidized bed.

[0015] [2] The method for reducing the molecular weight of an organic substance according to [1], wherein the temperature of the superheated steam introduced into the fluidized bed is higher than the temperature of the mixed gas introduced into the fluidized bed.

[0016] [3] The method for reducing the molecular weight of an organic substance according to [1] or [2] above, wherein the powder is a powder containing at least one selected from Fe, Ni, and Cr.

[0017] [4] A method for reducing the molecular weight of an organic substance according to any one of [1] to [3] above, wherein the organic substance includes rubber and elastomer.

[0018] [5] The method for reducing the molecular weight of an organic substance according to [4] above, wherein the rubber / elastomer includes a non-thermoplastic rubber.

[0019] The method for reducing the molecular weight of organic substances according to the present invention makes it possible to prevent undegraded organic substance components from adhering to the surface of the granular material constituting the fluidized bed. As a result, the function of the fluidized bed is not impaired midway through, and the reduction of organic substances into smaller molecules can be carried out efficiently and continuously.

[0020] This is a schematic diagram showing an example of a fluidized bed reactor used in the method for reducing the molecular weight of organic substances according to the present invention.

[0021] In one embodiment, the present invention relates to a method for reducing the molecular weight of an organic substance, comprising the steps of: mixing a gas containing carbon monoxide with a number of water vapor molecules exceeding the number of carbon monoxide molecules to cause a shift reaction, thereby obtaining a mixed gas containing hydrogen and carbon dioxide produced by the shift reaction, and excess water vapor not consumed in the shift reaction; and introducing an organic substance and the mixed gas into a fluidized bed in which granular material is flowing, and recovering low-molecular-weight products generated by a chemical reaction between the organic substance and the mixed gas, wherein superheated water vapor is further introduced into the fluidized bed. The following describes the matters that define the present invention in order.

[0022] [Mixed Gas] In this embodiment, two types of gases, a mixed gas and superheated steam, are used to reduce the molecular size of organic substances. Of these gases, the mixed gas contains hydrogen, carbon dioxide, and excess steam. The mixed gas is obtained by adding more steam molecules than carbon monoxide molecules to a gas containing carbon monoxide to cause a shift reaction. As mentioned above, the "shift reaction" is a chemical reaction represented by the following chemical formula (1). By utilizing the shift reaction, a mixed gas containing a high concentration of hydrogen can be produced at a lower cost compared to using commercially available hydrogen gas. The shift reaction for producing the mixed gas can be carried out by known methods and there are no special restrictions. Of the two types of gases mentioned above, superheated steam will be described later. CO + H ２ O→H ２ +CO ２ ... (1)

[0023] For the carbon monoxide-containing gas used in the shift reaction, it is preferable to use exhaust gas generated from a metallurgical furnace. A typical example of exhaust gas generated from a metallurgical furnace is converter gas generated from a converter where the decarburization process of the steel manufacturing process takes place. In addition, exhaust gas generated from other furnaces, such as a molten iron pretreatment furnace, a molten reduction furnace, or a shaft furnace, can also be used. Furthermore, a gas mixture of one or more of these exhaust gases may be used.

[0024] The typical composition of exhaust gas generated from metallurgical furnaces is 80-25 vol% carbon monoxide, 10-25 vol% carbon dioxide, 10-30 vol% nitrogen, and 0-20 vol% hydrogen. For exhaust gases with relatively low carbon monoxide concentrations and high nitrogen concentrations, such as blast furnace gas, at least a portion of the nitrogen may be removed to increase the carbon monoxide concentration before the shift reaction can be carried out. The mixed gas may contain nitrogen and other components derived from the exhaust gas.

[0025] If the hydrogen concentration in the gas mixture is too low, and the organic reforming reaction is carried out at a relatively low temperature, CO will be released into the low-molecular-weight product. ２ This makes it easier for residues to remain. Therefore, the hydrogen concentration is preferably 10 vol% or more, and more preferably 12 vol% or more. On the other hand, if the hydrogen concentration is too high, the decomposition rate of organic substances cannot be brought to a desirable level. Therefore, the hydrogen concentration is preferably 40 vol% or less, and more preferably 35 vol% or less.

[0026] If the concentration of carbon dioxide in the mixed gas is too low, hydrogen, a gaseous component with a lower calorific value compared to hydrocarbons and carbon monoxide, is more likely to remain in the low-molecular-weight products. Therefore, the concentration of carbon dioxide is preferably 10 vol% or higher, and more preferably 13 vol% or higher. On the other hand, if the concentration of carbon dioxide is too high, the decomposition rate of organic substances cannot be achieved at a desirable level. Therefore, the concentration of carbon dioxide is preferably 40 vol% or lower, and more preferably 35 vol% or lower.

[0027] "Excess water vapor" in the mixed gas refers to the water vapor that remains in the mixed gas without being consumed during the shift reaction, after being mixed with a gas containing carbon monoxide. To retain excess water vapor in the mixed gas, it is sufficient to add water vapor in a number exceeding the number of carbon monoxide molecules to the gas containing carbon monoxide. The method for producing the water vapor used in the shift reaction is not particularly limited.

[0028] When the concentration of excess steam in the mixed gas generated by the shift reaction is too low, the decomposition rate of the organic substance decreases, and the amount of heavy components generated, which causes a decrease in the fluidity of the powder, increases. Therefore, the concentration of excess steam is preferably 20 vol% or more, and more preferably 25 vol% or more. On the other hand, when the concentration of excess steam is too high, carbon dioxide tends to remain in the low molecular weight product, and the lower heating value (LHV) tends to decrease. Therefore, the concentration of excess steam is preferably 70 vol% or less, and more preferably 65 vol% or less.

[0029] In the method for reducing the molecular weight of an organic substance according to the present embodiment, the temperature and pressure of the mixed gas when introduced into the fluidized bed are not particularly limited. Since the shift reaction used to generate the mixed gas is an exothermic reaction, if the reaction temperature is too high, the shift reaction becomes difficult to proceed. Therefore, it is preferable that the reaction temperature of the shift reaction does not greatly exceed 400°C. Also, in order not to impose excessive pressure resistance on the reaction vessel that causes the shift reaction, it is preferable to carry out the shift reaction at atmospheric pressure. Therefore, when using the mixed gas obtained by the shift reaction as it is, it is preferable that the temperature of the mixed gas does not greatly exceed 400°C and the pressure does not differ greatly from atmospheric pressure. Here, "atmospheric pressure" refers to the pressure of air at sea level.

[0030] Although the reason why the mixed gas used in this embodiment is effective for the low-molecular-weight conversion of organic substances is not clear, it is probably due to the following reasons. When hydrogen coexists during the thermal decomposition of organic substances at high temperatures, hydrogen addition reactions and hydrocracking reactions to hydrocarbon species proceed, which is effective for suppressing heavyweight conversion and low-molecular-weight conversion. However, high temperatures are required for hydrocracking, and the problem is that the hydrogen consumption increases. On the other hand, the oxygen atoms contained in excess steam and carbon dioxide gas have the effect of oxidizing hydrocarbons, which may be called steam reforming and carbon gas reforming, respectively. Steam reforming and carbon dioxide reforming have the characteristic that the reaction temperature decreases as the carbon chain of the organic substance to be reformed becomes longer. Therefore, by using a mixed gas containing excess steam and carbon dioxide gas in addition to hydrogen gas, four reactions, namely hydrogen addition reaction, hydrocracking reaction, steam reforming, and carbon dioxide reforming, proceed simultaneously, and it is considered that the low-molecular-weight conversion of organic substances is promoted efficiently even at a relatively low reaction temperature.

[0031] [Organic Substances] In this embodiment, low-molecular-weight products generated by the chemical reaction between organic substances and the mixed gas are recovered. As the "organic substances" that are the targets of low-molecular-weight conversion in this embodiment, high molecular compounds such as synthetic resins such as polyethylene and polypropylene, or synthetic rubber materials are suitable. Specifically, for example, waste plastics, oily sludge, waste oil, biomass, etc. can be mentioned, and one or more of these can be targeted. Organic substances having 4 or less carbon atoms such as methane and ethanol may be included in the organic substances in this embodiment, but they are not the main targets of low-molecular-weight conversion.

[0032] There is no special limitation on the type of waste plastic, which is one of the targets of low-molecular-weight conversion in this embodiment. For example, industrial waste-based waste plastics and waste plastics subject to the Container and Packaging Recycling Law can be mentioned. More specifically, polyolefins such as polyethylene and polypropylene, thermoplastic polyesters such as polyamide and polyethylene terephthalate, elastomers such as polystyrene, thermosetting resins, synthetic rubbers, and styrofoam can be mentioned.

[0033] In this embodiment, "oil-containing sludge," which is one of the targets for molecular weight reduction, refers to a sludge-like mixture generated in the oil-containing wastewater treatment process, and generally contains about 30% to 70% by mass of water. Examples of oil content in oil-containing sludge include, but are not limited to, various mineral oils, natural and / or synthetic oils and fats, and various fatty acid esters. Furthermore, from the viewpoint of improving the handling properties of oil-containing sludge, it is preferable to reduce the water content in the oil-containing sludge to about 50% by mass or less beforehand using methods such as centrifugal separation.

[0034] Examples of waste oil targeted for molecular weight reduction in this embodiment include, but are not limited to, various used mineral oils, natural and / or synthetic oils and fats, and various fatty acid esters. A mixture of two or more of these waste oils may also be used. When targeting waste oil generated in the rolling process of a steel mill, it generally contains more than 80% by mass of water. It is preferable to reduce this water content in advance by methods such as specific gravity separation, in terms of handling.

[0035] Examples of biomass targeted for molecular weight reduction in this embodiment include, but are not limited to, wood such as sewage sludge, paper, construction waste wood, packaging and transportation waste wood, and thinned wood, as well as processed biomass such as refined waste fuel (RDF). Since biomass usually contains a large amount of moisture, it is preferable to dry it beforehand from the standpoint of energy efficiency.

[0036] The water contained in organic substances vaporizes into water vapor during the chemical reaction with the mixed gas. The generated water vapor is incorporated into the mixed gas in the fluidized bed, increasing the water vapor concentration in the mixed gas. Therefore, when adjusting the concentration of excess water vapor in the mixed gas produced by the shift reaction, it is preferable to determine the amount of water vapor to be added during the shift reaction by considering the amount of water vapor generated from the water contained in the organic substances.

[0037] [Fluidized Bed] In this embodiment, by introducing an organic substance and a mixed gas into a fluidized bed in which the granular material is flowing, a chemical reaction between the organic substance and the mixed gas is caused. Here, the "fluidized bed" (fluidized bed) refers to a form of a gas-phase reactor that fluidizes while suspending granular materials in the flow of gas blown from below and performs reactions, drying, absorption, etc. of reactants. As described above, by using a fluidized bed reactor as a reforming reactor that causes low molecular weight conversion of organic substances, it is possible to prevent the adhesion of organic substances, which is a problem in a flow-through fixed bed reactor. This is presumably because the temperature in the fluidized bed is almost uniform and heat transfer is very fast. Details of the structure of the fluidized bed reactor will be described later.

[0038] As the granular material constituting the fluidized bed used in this embodiment, it is preferable to use a material that is excellent in fluidity and thermal conductivity and stable against the low molecular weight conversion reaction of organic substances. Specifically, for example, iron-containing dust, mill scale, reduced iron powder, atomized iron powder, alumina powder, silica sand, etc. generated in the steelmaking process can be used, but the type of granular material is not limited to these. Also, a plurality of types of granular materials can be mixed and used.

[0039] When the particle size of the granular material constituting the fluidized bed is too small, there is a risk that the ventilation of the mixed gas and the superheated steam described later in the fluidized bed will be hindered. Therefore, the particle size of the granular material is preferably 0.01 mm or more in terms of D50, and more preferably 0.1 mm or more. On the other hand, when the particle size of the granular material constituting the fluidized bed is too large, there is a risk that smooth stirring of the organic substance in the fluidized bed will be hindered. Therefore, the particle size of the granular material is preferably 5 mm or less in terms of D50, and more preferably 1 mm or less. The D50 of the granular material can be measured by a sieving method or the like.

[0040] When the true density of the granular material constituting the fluidized bed is too small, the density difference from the ash of the organic substance is small, so it becomes difficult to separately collect the organic substance from the ash, and the separation of the granular material and the ash tends to be insufficient. Therefore, the true density of the granular material is 2.0 g / cm ３The above is preferable. On the other hand, if the true density of the powder is too high, the difference in specific gravity of the organic material being treated becomes large, making it difficult to flow the organic material and the powder in a state where they are sufficiently mixed. For this reason, the true density of the powder should be 8.0 g / cm³. ３ The following is preferable: When using a mixture of multiple types of powders and granules, the true density of the powders and granules can be the volume average value of the true densities of the individual powders and granules.

[0041] In a preferred embodiment, the granular material contains at least one selected from Fe, Ni, and Cr. Fe, Ni, and Cr are all active in the depolymerization reaction of organic substances, and the granular material functions as a catalyst, allowing the depolymerization reaction of organic substances to proceed with high efficiency. The form in which Fe, Ni, and Cr are contained in the granular material does not matter, whether it is a metal, oxide, or the like.

[0042] In this preferred embodiment, if the total content of Fe, Ni, and Cr in the granular material is too low, the true density of the granular material becomes low, making it difficult to separate the granular material scattered in the gas discharged from the fluidized bed reactor from the ash of organic matter. Therefore, the total content of Fe, Ni, and Cr in the granular material is preferably 20% by mass or more, and more preferably 30% by mass or more. On the other hand, if the total content of Fe, Ni, and Cr in the granular material is too high, the true density becomes too high, and the fluidity decreases. Therefore, the total content of Fe, Ni, and Cr in the granular material is preferably 90% by mass or less, and more preferably 80% by mass or less.

[0043] [Decomposition of Organic Substances into Low-Molecular-Weight Products] In this embodiment, organic substances and a mixed gas are introduced into a fluidized bed, and a chemical reaction between the organic substances and the mixed gas occurs inside the fluidized bed to decompose the organic substances into low-molecular-weight products, which are then recovered. As described above, in the decomposition method according to the present invention, four reactions—hydrogenation, hydrocracking, steam reforming, and carbon dioxide reforming—proceed simultaneously, thus efficiently decomposing organic substances into low-molecular-weight products. In reality, it is clear that a thermal decomposition reaction also proceeds in addition to these. Of these reactions, hydrocracking, steam reforming, carbon dioxide reforming, and thermal decomposition are endothermic reactions, while the hydrogenation reaction is an exothermic reaction. Therefore, the decomposition reaction of organic substances as a whole is an endothermic reaction, and it is necessary to supply reaction heat from an external source in order to keep the reaction proceeding continuously.

[0044] The excess water vapor contained in the gas mixture has a very high thermal conductivity and possesses an extremely high amount of heat, playing a crucial role in maintaining a high temperature inside the fluidized bed. Furthermore, in this invention, by causing a molecular decomposition reaction inside the fluidized bed, where the heat of reaction supplied from the outside is high, the molecular decomposition of organic substances can be carried out without waste. This prevents problems such as organic substances fusing together and causing blockages inside the fluidized bed.

[0045] [Superheated Steam] In this embodiment, superheated steam is further introduced into the fluidized bed. In this invention, two types of gases, a mixed gas and superheated steam, are used to demolecule organic substances. As mentioned above, "superheated steam" refers to steam heated to a temperature higher than the boiling point of water. The boiling point of water is, for example, 100°C under atmospheric pressure. As mentioned above, since the shift reaction used to generate the mixed gas is an exothermic reaction, if the reaction temperature is too high, the shift reaction will not proceed easily. For this reason, it is preferable that the reaction temperature of the shift reaction does not exceed 400°C. In contrast, the temperature of superheated steam is not restricted by the shift reaction, so it can be heated to any temperature. By using superheated steam in combination, demolecule organic substances proceeds with higher efficiency compared to when only the mixed gas containing excess steam is used.

[0046] In this embodiment, the reason why further introduction of superheated steam into the fluidized bed further promotes the demolecularization of organic substances is not entirely clear, but it is likely due to the following reasons. As is well known, liquid water has a very high specific heat, and therefore steam also exhibits very high thermal conductivity. Heat transfer by steam is usually convection, and at high temperatures, radiant heat transfer is also added, but in the case of superheated steam, a heat transfer called condensation heat transfer is also added. Here, "condensation heat transfer" is heat transfer that occurs when superheated steam adheres to the surface of an object as condensed water, transferring latent heat, and has 5 to 10 times the heating capacity compared to heated air. Also, since superheated steam is water molecules themselves, it has a very high hydrolysis capacity in an oxygen-free atmosphere. Due to the excellent heating capacity and hydrolysis capacity of superheated steam, it is thought that the demolecularization reaction of organic substances proceeds with high efficiency even at low temperatures and for short periods of time.

[0047] In this embodiment, the temperature of the superheated steam is not particularly limited, as long as it is higher than the boiling point of water. As will be described later, the thermal conductivity and hydrolysis capacity of superheated steam increase as the temperature of the superheated steam increases. For this reason, the temperature of the superheated steam is preferably 200°C or higher, more preferably 400°C or higher, and even more preferably 600°C or higher. On the other hand, there is no particular upper limit set for the temperature of the superheated steam, but since heating the superheated steam to a temperature above 1000°C requires a great deal of energy, the temperature of the superheated steam is preferably substantially 1000°C or lower.

[0048] In a preferred embodiment, the temperature of the superheated steam introduced into the fluidized bed is higher than the temperature of the mixed gas introduced into the fluidized bed. The thermal conductivity and hydrolysis capacity of the superheated steam increase as the temperature of the superheated steam increases. As mentioned above, the temperature of the superheated steam is not restricted by the shift reaction and can be heated to any temperature. In particular, if the temperature of the superheated steam is higher than the temperature of the mixed gas containing excess steam, the low-molecular-weight reaction of organic substances will further advance due to the high-temperature superheated steam introduced into the fluidized bed. The temperature of the superheated steam introduced into the fluidized bed is preferably 100°C or more higher than the temperature of the mixed gas introduced into the fluidized bed, and more preferably 200°C or more higher.

[0049] The pressure of the superheated steam is not particularly limited. As with mixed gases, it is preferable that the pressure of the superheated steam does not differ significantly from atmospheric pressure in order to avoid imposing excessive pressure resistance on the equipment that heats the superheated steam or on the fluidized bed reactor.

[0050] In this embodiment, it is preferable that the superheated steam is introduced into the fluidized bed via a different route than the excess steam that is introduced into the fluidized bed in the form of a mixed gas. This prevents a decrease in the temperature of the superheated steam before it is introduced into the fluidized bed. In this embodiment, the steam used for the shift reaction and the superheated steam may be supplied from the same source. In this case, the superheated steam can be branched, for example, into a different pipe from the steam used for the shift reaction, and additional heating can be performed after the branching.

[0051] [Low Molecular Weight Products] The low molecular weight products produced by the low molecular weight production method of organic substances according to this embodiment typically include light hydrocarbons with 1 to 4 carbon atoms and carbon monoxide. These gases can be suitably used as gaseous fuels. Furthermore, a portion of the low molecular weight products can be condensed to produce liquid fuels. The low heat of combustion (LHV) of the low molecular weight products obtained in this invention is approximately 6 Mcal / Nm³. ３ More than 10Mcal / Nm ３The following characteristics apply. This calorific value is comparable to that of natural gas, for example, and is characterized by higher flammability than natural gas due to its high carbon monoxide concentration. Because of these characteristics, the low molecular weight product obtained in this invention can be used, for example, as a fuel gas to replace city gas, which is the heat source for metallurgical furnaces used in steel mills.

[0052] Furthermore, the low-molecular-weight product obtained in this embodiment can be used not as fuel, but as a reducing agent in a blast furnace. As mentioned above, this low-molecular-weight product contains light hydrocarbons and carbon monoxide, which are components of natural gas, and both light hydrocarbons and carbon monoxide are effective as reducing agents for iron ore. Therefore, in the operation of a blast furnace, the amount of coke used, which is another reducing agent, can be reduced by blowing the low-molecular-weight product obtained in this embodiment into the blast furnace through a tuyeres or the like. This reduces the amount of carbon dioxide emitted from the blast furnace, which is also effective in reducing steelmaking costs.

[0053] [Rubber / Elastomer] In preferred embodiments, the organic substance includes a rubber / elastomer. Rubber / elastomer is a general term for polymer materials that are elastic. According to this embodiment, it becomes possible to reduce the molecular weight of non-thermoplastic rubber, which has been particularly difficult to reduce using conventional techniques.

[0054] The production volume of rubber and elastomers is increasing year by year. Consequently, the amount of rubber and elastomer waste generated during the production process or discarded by consumers is also continuously increasing. Rubber and elastomers are broadly classified into so-called rubber, which is not thermoplastic, and thermoplastic elastomers (thermoplastic elastomers: TPEs). Waste from thermoplastic elastomers can be recycled and has not become a major social problem. On the other hand, rubber molecules have a three-dimensional structure due to crosslinking through vulcanization. For rubber recycling, it is necessary to add regenerating agents to regain plasticity, causing depolymerization through plasticization of the crosslinked structure, cleavage of sulfur crosslinks, and cleavage of the molecular main chain. However, it is difficult for recycled rubber to maintain its original properties, and it is often processed through thermal recycling. Meanwhile, the calorific value of low-molecular-weight products obtained from the thermal decomposition of rubber is higher than that of waste plastics, and it is expected that more effective chemical recycling will be possible.

[0055] However, when attempting to reduce the molecular weight of rubber using conventional technology, heavy components and carbonaceous substances such as tar tend to mix into the low-molecular-weight product. Heavy components are unsuitable for use as fuel gas. Furthermore, carbonaceous substances adhere to the inside of fluidized bed reactors, piping, and the surface of powders and granules, reducing the exhaust capacity of the piping and decreasing the fluidity and catalytic performance of the powders and granules.

[0056] When the method for reducing the molecular weight of organic substances according to this embodiment is applied to rubber, the powerful hydrolysis ability of the superheated steam introduced into the fluidized bed in addition to the mixed gas promotes the molecular weight reduction reaction of the rubber. This suppresses the formation of heavy components and carbonaceous substances such as tar. Furthermore, since the superheated steam also decomposes carbonaceous substances adhering to the surface of the powder, the surface properties of the powder can be maintained, thereby preserving fluidity and a high catalytic effect.

[0057] As described above, the method for reducing the molecular weight of organic substances according to this embodiment is particularly effective in reducing the molecular weight of non-thermoplastic rubber. However, in this embodiment, thermoplastic elastomers may also be included in the rubber / elastomer contained in the organic substance. In this preferred embodiment, the content of rubber / elastomers in the organic substance is not particularly limited; the content only needs to be greater than zero, and the entirety of the organic substance may be rubber / elastomers. The form of the rubber / elastomer is not particularly limited, but from the viewpoint of shortening the reaction time inside the fluidized bed, it is preferable to introduce it into the reactor in a state where it has been crushed to about 2.5 cm or less.

[0058] In a more preferred embodiment, the organic substance includes non-thermoplastic rubber. Non-thermoplastic rubber encompasses all so-called rubber materials. Specific rubber materials include, but are not limited to, natural rubber, isoprene rubber, diene rubbers such as styrene-butadiene rubber, butadiene rubber, nitrile-butadiene rubber, chloroprene rubber, and butyl rubber; methylene-containing rubbers such as ethylene-propylene rubber, ethylene-vinyl acetate copolymer, chlorinated polyethylene, chlorosulfonated polyethylene, and acrylic rubber; and specialty rubbers such as hydrin rubber, urethane rubber, polysulfide rubber, silicone rubber, and fluororubber.

[0059] Specific rubber products using the above-mentioned rubber materials include automobile tires, which are discarded in large quantities every year. Waste conveyor belts used to transport ore and coal at steel mills and thermal power plants are also included. Both tires and conveyor belts often contain steel cords or steel wires to improve their strength. These steels remain intact without being altered by thermal decomposition within the fluidized bed, so they can be naturally separated by weight during processing and recovered at the bottom of the fluidized bed.

[0060] [Fluidized Bed Reactor] In this embodiment, it is preferable to use a fluidized bed reactor as the reforming reactor. Figure 1 is a schematic diagram showing an example of a fluidized bed reactor used in the method for reducing the molecular weight of organic substances according to this embodiment. In this fluidized bed reactor 1, the powder material is loaded above the gas dispersion plate 1b provided at the bottom of the cylindrical container. By supplying a gas 3 containing carbon monoxide and a number of water vapor molecules 4 exceeding the number of carbon monoxide molecules to the shift reactor 2 and causing a shift reaction, a mixed gas 5 containing hydrogen, carbon dioxide, and excess water vapor is produced.

[0061] By supplying the mixed gas 5 from the mixed gas inlet 1d located at the bottom of the fluidized bed reactor 1, the granular material floats and then repeatedly falls towards the bottom due to its own weight. This forms a fluidized bed 1a of granular material inside the fluidized bed reactor 1. By introducing organic material 6 into the fluidized bed 1a from the organic material inlet 1c located at the top of the fluidized bed reactor 1, a chemical reaction occurs between the organic material 6 and the mixed gas 5 inside the fluidized bed 1a. The low molecular weight products 7 generated by the chemical reaction are released to the outside from the low molecular weight product outlet 1e located at the top of the fluidized bed reactor 1 and recovered. The fluidized bed reactor 1 may be equipped with a heating mechanism (not shown) that can heat the container from the outside.

[0062] In this fluidized bed reactor 1, in addition to the mixed gas 5 supplied from the bottom, superheated steam 8 is further introduced into the fluidized bed 1a. This promotes the demolecularization reaction of organic substances 6 in the fluidized bed 1a, enabling more efficient demolecularization. It is preferable to introduce the superheated steam 8 into the fluidized bed reactor 1 not through the gas dispersion plate 1b at the bottom, but, for example, through the superheated steam inlet 1f located where the fluidized bed 1a exists, as shown in Figure 1. In this case, the temperature of the superheated steam 8 does not decrease due to mixing with the mixed gas, so the temperature of the superheated steam 8 can be maintained at a high temperature while being introduced into the fluidized bed 1a.

[0063] The flow velocity of the mixed gas 5 blown from the gas dispersion plate 1b toward the fluidized bed 1a is preferably adjusted to a range that maintains a good dispersion state of the powder and granules. If the flow velocity of the mixed gas 5 is too low, the fluidity of the fluidized bed 1a decreases, hindering the progress of the low-molecular-weight reaction. Therefore, the flow velocity of the mixed gas 5 is preferably 0.05 m / s or higher. On the other hand, if the flow velocity of the mixed gas 5 is too high, although there is no problem with the fluidity of the fluidized bed 1a, the flow velocity of the low-molecular-weight product 7 and excess mixed gas 5 discharged from the fluidized bed reactor 1 increases, increasing the amount of powder and granules scattered to the outside from the low-molecular-weight product outlet 1e. Furthermore, as will be described later, when the organic substance 6 is supplied from the top of the fluidized bed reactor 1, the particle size of the organic substance 6 also needs to be large, which reduces the reaction efficiency of the low-molecular-weight reaction. Therefore, the flow velocity of the mixed gas 5 is preferably 2.0 m / s or less.

[0064] In this embodiment, the organic substance 6, such as plastic, is reduced in molecular size, and the number of molecules doubles. Therefore, it should be noted that the flow velocity of the gas containing the low-molecular-weight product 7 discharged from the fluidized bed reactor 1 will be approximately twice that of the mixed gas 5. For example, if the flow velocity of the mixed gas 5 is 0.05 m / s, the flow velocity of the gas containing the low-molecular-weight product 7 will be approximately 0.1 m / s. Also, if the flow velocity of the mixed gas 5 is 2.0 m / s, the flow velocity of the gas containing the low-molecular-weight product 7 will be approximately 4.0 m / s.

[0065] As for the method of supplying the organic substance 6 into the fluidized bed reactor 1, liquid organic substances such as oily sludge and waste oil can be sprayed using a spray nozzle or the like, and the supply position can be anywhere in the fluidized bed reactor 1. On the other hand, in the case of solid organic substances 6 such as waste plastics, biomass, and rubber / elastomers, it is common to supply them from the top of the fluidized bed reactor 1, but they can also be supplied to the top of the gas dispersion plate 1b by gas transport. When supplying solid organic substances 6 from the top of the fluidized bed reactor 1, it is convenient to let the organic substance 6 fall by gravity. However, in this case, it is preferable to mold the supplied solid organic substance 6 to a particle size and density that does not scatter, while at the same time selecting a particle size that does not reduce the reaction efficiency. Furthermore, when transporting organic substances 6 by gas, if air is used, so-called combustion will occur in the reactor due to the oxygen contained in the air, so it is preferable to use a mixed gas or exhaust gas containing carbon monoxide instead of air.

[0066] When a solid organic substance 6 is supplied from the top of a fluidized bed reactor 1 and allowed to fall, the particle size at which the supplied solid organic substance 6 does not scatter depends on the density of the organic substance 6 and the flow rate of the gas containing the low molecular weight product 7. For example, if the true density of the solid organic substance 6 is 1 g / cm³ ３ Therefore, when the flow velocity of the gas containing the low molecular weight product 7 is about 0.1 m / s, it is preferable that the particle size of the molded solid organic material 6 be between 2.0 mm and 6.0 mm. Also, when the flow velocity of the gas containing the low molecular weight product 7 is about 4.0 m / s, it is preferable that the particle size of the molded solid organic material 6 be between 15 mm and 20 mm.

[0067] The gas containing low-molecular-weight products 7 discharged from the fluidized bed reactor 1 contains some of the granular material constituting the fluidized bed 1a, as well as ash generated from the decomposition of organic materials 6 such as waste plastics, rubber, and elastomers. These contaminants can be collected by a dust collector (not shown) installed downstream of the fluidized bed reactor 1. The granular material has a true density of 3.0 g / cm³, which is higher than the true density of granular material commonly used in fluidized beds. ３When using granular material of a certain degree, the granular material and the ash of organic matter 6 can be collected in a separated state in the dust collector. This makes it easy to return the separated granular material back to the fluidized bed 1a from the granular material inlet 1h shown in Figure 1, and prevents the granular material from being diluted by the ash, which is inert to the low molecular weight reaction. On the other hand, if the true density of the granular material is too high, as mentioned above, the fluidity of the granular material decreases, or the difference in specific gravity between it and waste plastics, rubber, and elastomers becomes too large, making it difficult to perform fluid agitation properly. Therefore, the true density of the granular material should be 8.0 g / cm³. ３ It is preferable that the following be the case.

[0068] In this embodiment, the action of the fluidized bed 1a and superheated steam 8 makes it difficult for heavy components and carbonaceous substances such as tar, which are components of the undecomposed organic matter 6, to be generated. Nevertheless, during long-term operation, small amounts of these components may be generated and remain inside the fluidized bed 1a or adhere to the surface of the powder or granular material. Also, when waste tires or waste conveyor belts are used as rubber or elastomer, metals such as steel cords and steel wires will remain inside the fluidized bed 1a without being decomposed. Because these heavy components, carbonaceous substances such as tar, and metals have a high specific gravity, they will not be discharged from the low-molecular-weight product outlet 1e along with the low-molecular-weight products 7, but will remain inside the fluidized bed 1a. Furthermore, some of the ash, which is the residue of the low-molecular-weight reaction, may also remain inside the fluidized bed 1a. These residues can be discharged together with the powder or granular material from the residue outlet 1g shown in Figure 1 during the low-molecular-weight reaction or when the operation is stopped. If residue can be separated from the discharged material and the remaining powder can be reused, it can be returned to the fluidized bed 1a through the powder inlet 1h.

[0069] The embodiments for carrying out the present invention will be described in more detail using examples. However, the scope of the present invention is not limited to the following examples.

[0070] [Example of Invention 1] A gas containing carbon monoxide, with an average composition of H ２ :12vol%, CO:54vol%, CO ２ : 17 vol%, H ２ O: 1 vol%, N２ A converter gas with a concentration of 16 vol% was used. A branch pipe for laboratory testing was installed in the gas discharge piping of the gas holder that temporarily stores the converter gas, allowing for the extraction of a small flow rate of converter gas through this branch pipe. Downstream of this branch pipe, a flow control valve, a steam mixer, a preheater for preheating the mixture of converter gas and steam, a shift reactor for initiating the shift reaction, and a fluidized bed reactor were arranged in this order. Of these, the shift reactor was packed with an Fe-Cr-based high-temperature shift catalyst.

[0071] A fluidized bed reactor with an inner diameter of 66 mm and capable of being heated from the outside was prepared. Piping was connected to the bottom of the fluidized bed reactor so that the entire amount of gas generated in the shift reactor could be supplied to the fluidized bed reactor. A gas dispersion plate was installed at the bottom of the fluidized bed reactor, and on top of the gas dispersion plate, a mixture of converter dust mainly composed of Fe generated in decarburization blowing and silica sand was prepared as a powder in a mass ratio of 1:2, resulting in a true density of 3.0 g / cm³. ３ Powdered material, adjusted to the following specifications, was loaded. The D50 of the powdered material was 0.5 mm. The temperature of the powdered material loaded inside the fluidized bed reactor was maintained at 600°C by external heating, regardless of whether superheated steam was introduced or not. A circle feeder type quantitative feeding device was installed at the top of the fluidized bed reactor so that organic material could be introduced into the fluidized bed by dropping it in. A superheated steam inlet was provided at a height of 1 / 3 of the way up from the bottom of the fluidized bed reactor, allowing for the introduction of superheated steam into the fluidized bed independently of the mixed gas used in the shift reaction.

[0072] Next, the converter gas extracted through the branch pipe is supplied to the steam mixer at a flow rate of 1.3 NL / min, and the pressure is 10 kg / cm². ２ G was mixed with steam at a flow rate of 1.7 NL / min. Next, the converter gas and steam mixture was heated to 300°C in a preheater and then introduced into the shift reactor. The composition of the mixed gas obtained by the shift reaction was H ２ :26vol%, CO:2vol%, CO ２ : 28 vol%, H ２ O (excess water vapor): 37 vol%, N ２The concentration was 7 vol%. The temperature of the mixed gas at the outlet of the shift reactor was 400°C. This mixed gas was introduced at a flow rate of 3.0 NL / min from the bottom of the fluidized bed reactor through the gas dispersion plate. On the other hand, the same pressure of 10 kg / cm² as the steam used in the shift reaction was applied. ２ The steam from G was heated to 600°C using an electric heater to become superheated steam, and then introduced into the fluidized bed inside the fluidized bed reactor at a flow rate of 0.6 NL / min through a port, which is a different path from the gas dispersion plate, which is the path for the mixed gas.

[0073] Next, using a quantitative feeding device, waste plastic with a particle size of 8 mm and rubber conveyor belt cut into cube shapes with sides of approximately 10 mm were supplied to the fluidized bed reactor at a supply rate of 5.0 g / min each, and the low-molecular-weight material breakdown was carried out continuously for 1 hour. After that, the supply was stopped, and the heating of the fluidized bed reactor was stopped to allow the powder and granules to cool. During this time, the low-molecular-weight products recovered from the top of the fluidized bed reactor and cooled by the gas cooler were analyzed to determine their composition, generation rate, and lower heat of combustion (LHV). The generated liquid collected using a liquid fuel collector installed at the bottom of the gas cooler was also analyzed, and its type and generation rate were determined in the same way as the low-molecular-weight products. Furthermore, the generated solids separated and recovered from the cooled powder and granules were also analyzed. These analytical results are summarized in Table 1.

[0074] According to Table 1, the composition of the recovered low molecular weight products consisted of molecules with 1 to 4 carbon atoms, while those with 5 or more carbon atoms were below the detection limit. Furthermore, the low heat of combustion (LHV) of the low molecular weight products was 5.9 kcal / Nm³. ３ The gas content was equivalent to or greater than that of so-called coke gas. The recovered liquid was oil with a calorific value of 10,373 kcal / kg, and the proportion of ash and water, as well as the kinematic viscosity, were all equivalent to that of heavy oil No. 1. The flash point of this oil was a relatively low 49°C, equivalent to that of light oil. The recovered solid was completely carbonized carbon black, with a production rate of 1.5 g / min. This carbon black is thought to have originated from a waste conveyor belt.

[0075] [Example 2 of Invention] The test was conducted under the same conditions as in Example 1, except that the organic material fed into the fluidized bed reactor was limited to a rubber conveyor belt cut into cube shapes with sides of approximately 10 mm, and the supply rate was set to 10 g / min. The amount of low molecular weight product obtained was less than in Example 1, but its low heat of combustion (LHV) was 6.3 kcal / Nm³. ３ As a result, the gas had an even higher calorific value than that of Invention Example 1. On the other hand, the amount of oil, which is the liquid component produced, and carbon black, which is the solid component produced, was approximately double that of Invention Example 1.

[0076] [Example 3 of Invention] The test was conducted under the same conditions as in Example 1 of Invention, except that the organic material fed into the fluidized bed reactor was limited to waste plastic with a particle size of 8 mm, and the supply rate was set to 10 g / min. The amount of low molecular weight product obtained increased compared to Example 1 of Invention. In addition, it contained hydrocarbons with a carbon content of 5 or more, and its lower heat of combustion (LHV) was 4.9 kcal / Nm³. ３ The resulting gas had a slightly lower calorific value compared to Invention Example 1. The generated liquid was mainly tar, but no tar was observed to adhere to the pipes or granular materials.

[0077] [Comparative Example 1] The test was conducted under the same conditions as in Invention Example 1, except that the supply of superheated steam to the fluidized bed reactor via the port was stopped. Compared to Invention Examples 1, 2, and 3, the composition of the obtained low molecular weight product showed an increase in the amount of hydrocarbons with a carbon content of 5 or more, and the low heat of combustion (LHV) was 2.5 kcal / Nm³. ３ The resulting gas had an even lower calorific value than that of Invention Example 3. Tar deposits were observed on the inner wall surface of the piping leading to the liquid fuel collector located at the bottom of the gas cooler. Tar deposits were also observed on the surface of the powder. The recovered solid was carbon black, and the production rate was 1.7 g / min.

[0078] [Comparative Example 2] The test was conducted under the same conditions as in Invention Example 3, except that the supply of superheated steam to the fluidized bed reactor via the port was stopped. In Comparative Example 2, where superheated steam was not used and the supplied organic substance did not contain rubber or elastomer, the low molecular weight reaction did not proceed, and the low heat of combustion (LHV) of the low molecular weight product was 3.2 kcal / Nm³. ３The levels were low. In addition, tar buildup was observed on the inner walls of the pipes.

[0079] [Comparative Example 3] The test was conducted under the same conditions as in Comparative Example 2, except that silica sand alone was used as the granular material loaded into the fluidized bed, instead of a mixture of converter dust and silica sand. In Comparative Example 3, which did not use superheated steam and used granular material that did not contain Fe, Ni, and Cr, there was no acceleration of the decomposition reaction due to the catalytic effect of the granular material. In addition, the proportion of hydrocarbons with four or fewer carbon atoms in the low molecular weight products and the low heat of combustion (LHV) of the low molecular weight products were the lowest values ​​among the examples. Tar adhesion to the inside of the pipes was also observed.

[0080]

[0081] The test results shown in Table 1 show that when superheated steam is introduced into a fluidized bed according to the method for reducing the molecular weight of organic substances according to the present invention, the reaction of reducing the molecular weight of organic substances is accelerated compared to conventional techniques that do not use superheated steam. Furthermore, it can be seen that a high low heat of combustion (LHV) is obtained for the low molecular weight products, and tar does not adhere to the pipes or powders. Moreover, in the preferred embodiments shown in Invention Examples 1 and 2, in which the introduced organic substance includes rubber and elastomer, the decarbonization reaction is further accelerated, tar formation is suppressed, and a value of 5.0 kcal / Nm³ is obtained. ３ It can be seen that low-molecular-weight products with a high lower heat of combustion (LHV) exceeding this value can be obtained.

[0082] 1. Fluidized Bed Reactor 1a. Fluidized Bed 1b. Gas Dispersion Plate 1c. Organic Material Inlet 1d. Mixed Gas Inlet 1e. Low Molecular Weight Product Outlet 1f. Superheated Steam Inlet 1g. Residue Outlet 1h. Powder / Granular Material Inlet 2. Shift Reactor 3. Gas Containing Carbon Monoxide 4. Steam 5. Mixed Gas 6. Organic Material 7. Low Molecular Weight Product 8. Superheated Steam

Claims

1. A method for reducing the molecular weight of an organic substance, comprising the steps of:

1. Mixing a gas containing carbon monoxide with water vapor in a number exceeding the number of carbon monoxide molecules to cause a shift reaction, thereby obtaining a mixed gas containing hydrogen and carbon dioxide produced by the shift reaction, and excess water vapor not consumed by the shift reaction; and 2. Introducing an organic substance and the mixed gas into a fluidized bed in which granular material is flowing, and recovering low molecular weight products generated by a chemical reaction between the organic substance and the mixed gas, wherein superheated water vapor is further introduced into the fluidized bed.

2. The method for reducing the molecular weight of an organic substance according to claim 1, wherein the temperature of the superheated steam introduced into the fluidized bed is higher than the temperature of the mixed gas introduced into the fluidized bed.

3. The method for reducing the molecular weight of an organic substance according to claim 1 or 2, wherein the granular material is a granular material containing at least one selected from Fe, Ni, and Cr.

4. A method for reducing the molecular weight of an organic substance according to any one of claims 1 to 3, wherein the organic substance includes rubber and elastomers.

5. The method for reducing the molecular weight of an organic substance according to claim 4, wherein the rubber / elastomer includes a non-thermoplastic rubber.

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