Method for producing methane-containing gas and apparatus therefor

Abstract

To provide a method that solves the following problems, wherein although autothermal reforming reaction is mentioned as a method for converting oil content into methane gas, there is a problem that methane purity is low because hydrogen, carbon monoxide, and carbon dioxide are generated in addition to methane gas, and furthermore, when reformed gas is passed through a basic aqueous solution to remove carbon dioxide for further increasing the methane purity, there is also a problem that water-insoluble carbonates are generated and piping through which the reformed gas passes is blocked.SOLUTION: A method for producing a methane-containing gas of the present invention includes converting oil content and water vapor into a mixed gas mainly consisting of hydrogen, carbon monoxide, methane, and carbon dioxide by autothermal reforming reaction, then separating unreacted oil content, water, and tar by gas-liquid separation, and further converting the hydrogen, carbon monoxide, and carbon dioxide contained in the reformed gas into methane gas by methanation. The method for producing a methane-containing gas includes removing residual carbon dioxide with sodium hydroxide or potassium hydroxide supported on a high specific surface area support to obtain a methane-containing gas having a methane purity of 60% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for producing a high-purity methane-containing gas using oil as a raw material. [Background technology]

[0002] (Current status of fuel gas production using oil as a raw material) Fuel production from biomass is attracting attention with the aim of conserving petroleum resources and reducing carbon dioxide emissions. Among these, waste oil such as used cooking oil has the advantages of being low in elements other than carbon, hydrogen, and oxygen, having a high energy density compared to other biomass, and being relatively easy to collect since it is often generated in densely populated areas.

[0003] Methods for producing methane from oils such as waste oil include methane fermentation, in which anaerobic microorganisms convert oils into methane; dry distillation gasification, in which oils are thermally decomposed and gasified under low-oxygen or oxygen-free conditions; and steam reforming, in which oils are brought into contact with water in the presence of a catalyst to promote gasification.

[0004] Of these, methane fermentation produces methane through microbial decomposition of biomass at room temperature and pressure. However, the reaction is slow, and the amount of methane produced varies depending on the type of bacterial flora and biomass, as well as the added components necessary for microbial growth.

[0005] In addition, methods of gasifying oils by carbonization or steam reforming enable stable, large-scale production of gas fuel at a relatively low cost. However, oils often have a carbon number of 16 to 18, and the gas conversion rate, i.e., the ratio of the amount of carbon gasified to the amount of carbon in the reforming feedstock, is lower than that of lower hydrocarbons such as naphtha. Another issue is that in addition to methane, hydrogen, carbon monoxide, and carbon dioxide are produced, and unreacted water vapor and oil vapor are also present.

[0006] Taking these factors into consideration, for example, Patent Document 1 proposes a method of gasifying oil through an autothermal reforming reaction in which a required amount of air is introduced into a reaction system together with steam at 600°C to 800°C in a reaction tube filled with a catalyst. Patent Document 2 also discloses a gas production device in which water to which oil and a small amount of potassium carbonate have been added is heated to 300°C and introduced into a methane gas production reaction tube, where it is then heated to around 1500°C to be converted into methane. Furthermore, Patent Document 3 proposes a method of removing carbon dioxide by bringing the reformed gas into contact with an aqueous sodium hydroxide solution in order to increase the concentrations of hydrogen and methane in the reformed gas. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-179542 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-275538 [Patent Document 3] Patent No. 7048125 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the case of Patent Document 1, the main component of the reformed gas obtained by the autothermal reforming reaction is methane, which is the raw material for city gas, and also contains large amounts of hydrogen, carbon monoxide, and carbon dioxide, resulting in low methane purity, making it difficult to use such reformed gas as an alternative fuel to natural gas or city gas. Furthermore, when a gas-liquid separator is installed downstream of the reaction tube to separate the unreacted water and oil from the reformed gas in the autothermal reforming reaction, the gas-liquid separator contains tar as well as water and oil. This makes it difficult to subject the water and oil recovered by the gas-liquid separator to the autothermal reforming reaction again, and also poses the problem of high disposal costs when discarding the water and oil.

[0009] In the case of Patent Document 2, the temperature inside the methane gas production reaction tube rises to around 1500°C, which not only increases the amount of energy input required for methane production but also raises concerns that the methane gas production reaction tube may be prone to deterioration. Furthermore, when potassium carbonate is used to act as a catalyst, the catalyst must be constantly added to the feed water, posing a problem that hinders industrialization. In the case of Patent Document 3, when the reformed gas is brought into contact with a basic solution such as an aqueous sodium hydroxide solution in order to increase the hydrogen and methane concentrations in the reformed gas, water-insoluble carbonates precipitate, causing blockage of the reformed gas piping, and a large amount of basic wastewater is generated, which requires a lot of effort, labor, and cost for its proper treatment. Therefore, in order to solve the above problems, an object of the present invention is to provide a method or apparatus that can increase the conversion rate of oil to methane, which is applicable to industrial applications, while timely removing tar, carbon, or carbon dioxide without causing any adverse effects. [Means for solving the problem]

[0010] In the method for achieving the above-mentioned object, means 1 includes: The raw materials are waste oil, such as used tempura oil from ordinary households, and water, such as tap water. It is also preferable to supply oxygen from an oxygen source at an appropriate time to partially oxidize the oil and break it down into lower molecular weight compounds. The process involves subjecting these feedstocks to an autothermal reforming reaction to produce an autothermal reforming reaction gas containing hydrogen, carbon monoxide, methane, and carbon dioxide. In this process, an autothermal reforming catalyst is used, and it is preferable to have a hydrogen source that periodically reduces the autothermal reforming catalyst. In the above-mentioned autothermal reforming reaction gas generation process, if the generated reformed gas contains unreacted oil, it is preferable to absorb the oil in an oil absorbent, and at the same time, the tar and water contained in the generated reformed gas are condensed and removed using an oil absorbent or the like, while the reformed gas is passed through a gas-liquid separation process to separate it. The hydrogen, carbon monoxide, and carbon dioxide contained in the reformed gas separated in the gas-liquid separation process are converted into a product gas mainly composed of methane by a methanation catalyst, and the product gas is passed through a methanation process to increase the amount of the methane component. Subsequently, in order to remove carbon dioxide contained in the methanated gas obtained in the methanation step, the gas is passed through a carbon dioxide removal step in which carbon dioxide is removed. By passing through the above-mentioned series of systematic steps, a high-purity methane-containing gas can be produced.

[0011] In addition, in the fourth means of the apparatus for achieving the above-mentioned object, an autothermal reforming reaction tube is provided in which an autothermal reforming reaction catalyst layer is disposed below an alumina layer that is heated to a high temperature, and a heat source that controls heating to a high temperature is attached. Note that an alumina layer may also be disposed below the autothermal reforming reaction catalyst layer. The reactor is provided with a raw material supply unit that individually supplies the raw material oil and water to the autothermal reforming reactor column using a liquid feed pump or the like while controlling the amounts of each. Also provided is an oxygen supply unit for partially oxidizing oil content supplied to the autothermal reforming reactor while controlling the flow rate of oxygen. Furthermore, the system includes a first hydrogen supply unit that supplies hydrogen to the autothermal reforming reactor at an appropriate time while controlling the flow rate, thereby reducing the autothermal reforming catalyst in the reactor. A first gas-liquid separation unit is installed that receives the autothermal reforming reaction gas generated in the above-mentioned autothermal reforming reaction tube in an environment of 0°C to 30°C, absorbs oil and tar, and delivers the reformed gas. The reformed gas is received from the first gas-liquid separation section, and a heat source is attached that can heat the reformed gas to a high temperature while controlling the internal temperature. The methanation cylinder has a methanation catalyst layer sandwiched between alumina layers. The system is also equipped with a second hydrogen supply source that is introduced to remove carbon remaining inside the methanation column and to activate the catalyst. The first hydrogen supply unit can also serve as this second hydrogen supply source. The system has a second gas-liquid separation section that receives the moisture-containing methanated gas produced in the methanation column and delivers the methanated gas components obtained by separating the gas components from the moisture. The system receives the post-methanation gas components from the second gas-liquid separation unit and oxygen from the oxygen supply unit, is equipped with a heat source that controls the internal temperature within the range of 0°C to 50°C, and has a carbon dioxide removal column filled with activated carbon. With the above-described configuration, the present invention can provide a production apparatus capable of producing a methane-containing gas with high purity.

[0012] The production method of the present invention described above provides a technology that enables the production of high-purity methane from waste oil and other materials discarded from ordinary households. This method is also an invention that provides a system that plays a key role in a recycling-oriented society. In particular, the individual technologies of autothermal reforming and methanation are well known. Autothermal reforming technology is used to produce hydrogen. Methanation is also known as a technology that produces methane from carbon dioxide and hydrogen, aiming for a decarbonized society. However, there are still only a few examples of technology for producing methane from waste cooking oil, and practical application is lagging behind. The inventors of this invention conducted research and development on the theme of how to produce methane gas from waste cooking oil that can be used for purposes such as city gas. As a result, they came up with the concept of generating practical methane gas by combining technologies that generate hydrogen and methane-containing gas from oil and water as raw materials through a steam reforming catalyst, and then purifying the generated gas using methanation technology. Based on this concept, they conducted experiments and were able to establish a practical method. They also invented a device that realizes this method. [Effects of the Invention]

[0013] The method for producing a methane-containing gas of the present invention has provided a method for producing high-purity methane gas that can increase the conversion rate to methane while removing tar, carbon, or carbon dioxide in a timely manner. Also, the apparatus for producing a methane-containing gas of the present invention has provided an apparatus that can produce high-purity methane gas that increases the conversion rate to methane while maintaining the activation of the two reaction tubes, such as by reducing the reforming catalyst in a timely manner and removing carbon.

[0014] (Other means to solve the problem) In the method or apparatus for achieving the above object, means 2 or 5: In the method or apparatus for producing a high-purity methane-containing gas according to Means 1, in which the carbon dioxide removing material is activated carbon that supports at least one of sodium hydroxide and potassium hydroxide so as to satisfy the following mathematical formula, the purity of the methane gas can be increased by specifying the following:

number

number

[0015] In addition, in the present invention, a gas-liquid separation section is installed downstream of the reaction tube where the autothermal reforming reaction of the oil takes place, and unreacted oil, tar, and water are separated from the gas components. Separation is achieved by installing an oil absorbent in the gas-liquid separation section, which allows the separation of water, oil, and tar. This not only makes it possible to return the separated water to the autothermal reforming reaction tube, but also simplifies disposal when it is necessary to discard the system.

[0016] Furthermore, in the present invention, the oil absorbent that has absorbed oil and tar can be used as a boiler fuel, etc. Therefore, for example, when a burner is used as a heat source for an autothermal reforming reaction or methanation, the oil absorbent that has absorbed oil and tar can be supplied as fuel. [Brief explanation of the drawings]

[0017] [Figure 1] Fig. 1 shows an overall schematic diagram of the high-purity methane production apparatus of the present invention, specifically, a process flow diagram showing the autothermal reforming reaction step of oil, the gas-liquid separation step, the methanation step, the carbon dioxide removal step, and the water vapor removal step. [Figure 2] Figure 2 shows an example of an apparatus in which three pairs of autothermal reforming reactors and first gas-liquid separation units are installed in parallel in an apparatus in which an autothermal reforming reactor and a first gas-liquid separation unit are paired for oil. [Figure 3] Figure 3 shows an example of an apparatus in which two pairs of methanation columns and second gas-liquid separation sections are installed in parallel in an apparatus in which a methanation column and a second gas-liquid separation section are paired together. That is, it is an explanatory diagram showing a process flow for simultaneously removing carbon from the methanation catalyst in the methanation column and activating the catalyst. [Figure 4]Figure 4 shows an example of an apparatus in which two pairs of carbon dioxide and water vapor removal steps are installed in parallel in an apparatus with a pair of carbon dioxide and water vapor removal steps. That is, it is an explanatory diagram showing the process flow of a carbon dioxide removal column and a water vapor removal column that sequentially remove carbon dioxide and water vapor contained in methanation gas, and that can operate only one column while the other can be stopped for replacement work, etc. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described with reference to Figures 1 to 4, with reference numerals indicating the main parts, by way of example. Note that this is intended to illustrate one example of an embodiment of the present invention, and is not intended to limit the scope of the invention.

[0019] (Overview of the autothermal reforming reaction process and gas-liquid separation process) Figure 1 shows a schematic diagram of the entire system, including the autothermal reforming reaction process for oil, gas-liquid separation process, methanation process, carbon dioxide removal process, and water vapor removal process. The autothermal reforming reaction of oil, such as waste cooking oil, begins with a liquid feed pump 1a introducing oil and water via a liquid feed pump 1b through pipe 2 and valve 3 into an autothermal reforming reactor 5. The oil introduced into the autothermal reforming reactor 5 first comes into contact with alumina balls 61, which have been preheated to a temperature between 300°C and 900°C by a heat source 4, where it is vaporized. The oil then comes into contact with an autothermal reforming catalyst 62, which has been preheated to a temperature between 450°C and 900°C by the heat source 4, suitable for the autothermal reforming reaction. The resulting gas is converted into a reformed gas primarily composed of hydrogen, carbon monoxide, carbon dioxide, and methane.

[0020] At this time, oxygen is introduced from an oxygen cylinder 7 through a pipe 8 and a mass flow controller 9 to partially oxidize the oil. This promotes the breakdown of the oil into lower molecular weight molecules, thereby increasing the gas conversion rate in the autothermal reforming reaction process.

[0021] The reformed gas containing unreacted oil, tar, and water vapor passes through alumina balls 63 and is introduced into gas-liquid separation section 10. The temperature inside gas-liquid separation section 10 is controlled to be below room temperature, and the reformed gas and water vapor at its saturated vapor pressure are transferred to the next step, the methanation step, through valve 11 and piping 12.

[0022] Meanwhile, unreacted oil and tar are absorbed by oil absorbent material 13 installed in gas-liquid separation section 10. Furthermore, water that condenses in gas-liquid separation section 10 accumulates without being absorbed by oil absorbent material 13, but can be discharged outside the system by opening valve 14. In addition, by making the bottom of gas-liquid separation section 10 removable, oil absorbent material 13 can be replaced as needed, and unreacted oil and tar can also be easily discharged outside the system.

[0023] In addition to unreacted oil, tar, a by-product of the autothermal reforming reaction, adheres to the alumina balls 61, 63, and autothermal reforming catalyst 62 inside the autothermal reforming reactor 5. This not only reduces the activity of the autothermal reforming catalyst 62, but also causes pressure loss. In addition, when replacing the alumina balls 61, 63, and autothermal reforming catalyst 62 inside the autothermal reforming reactor 5, the tar adheres and makes removal difficult. Even if new alumina balls and catalyst are installed after removal, there is concern that tar remaining on the inner wall of the autothermal reforming reactor 5 may cause pressure loss and a decrease in catalyst activity.

[0024] Therefore, before the activation inside the autothermal reforming reaction tube 5 decreases, the heat source 4 is heated to about 500°C while oxygen is supplied from the oxygen cylinder 7 to the autothermal reforming reaction tube 5 via piping 8 and mass flow controller 9, thereby burning off the unreacted oil and tar. Then, while the temperature is being raised by the heat source 4, hydrogen is introduced from the hydrogen cylinder 15 via piping 16, mass flow controller 26 and valve 17, thereby reactivating the individual autothermal reforming reaction catalysts 62.

[0025] Furthermore, when replacing the alumina balls 61, 63, and autothermal reforming reaction catalyst 62 inside the autothermal reforming reaction tube 5, the alumina balls and catalyst installed inside the autothermal reforming reaction tube 5 can be easily removed, and even after installing new alumina balls and catalyst, pressure loss and a decrease in catalyst activity caused by tar adhering to the inner wall of the autothermal reforming reaction tube 5 can be prevented.

[0026] In actual operation, by installing at least three autothermal reforming reaction tubes, such as autothermal reforming reaction tubes 5a, 5b, and 5c as shown in Figure 2, it is possible to operate the autothermal reforming reaction in one tube, the unreacted oil and tar by burning and removing the other tube, and the autothermal reforming reaction catalyst in another tube in parallel.

[0027] That is, for example, when oil is supplied by liquid feed pump 1a and water by liquid feed pump 1b through pipe 2 and valve 3a to autothermal reforming reactor 5a, which has been heated to a temperature suitable for the autothermal reforming reaction by heat source 4a, and the autothermal reforming reaction is carried out, valves 3b and 3c are closed. The reformed gas produced in autothermal reforming reactor 5a enters gas-liquid separation section 10a and is transferred to the downstream methanation step through valve 11a. At this time, valves 14a, 11b, and 11c are closed.

[0028] Meanwhile, oxygen is introduced into the autothermal reforming reactor 5b from the oxygen cylinder 7 via piping 8 and mass flow controller 9b while being heated to a set temperature by the heat source 4b. This raises the temperature inside the autothermal reforming reactor 5b, and burns off the oil and tar adhering to the alumina balls 61b, 63b, and autothermal reforming catalyst 62b. Meanwhile, the moisture that becomes water vapor is discharged to the gas-liquid separator 10b, whose temperature is adjusted to below room temperature. At this time, the valve 14b is left open, allowing the carbon dioxide produced by combustion and the oxygen supplied from the oxygen cylinder 7 to be released outside the system through the valve 14b.

[0029] The oil absorbent 13b in the gas-liquid separation section 10b contains oil and tar discharged from the autothermal reforming reaction tube 5b during the autothermal reforming reaction, but is removed from the bottom of the gas-liquid separation section 10b and then replaced with a new oil absorbent. Note that the oil absorbent 13b containing oil and tar can be reused by washing it with an organic solvent such as acetone or petroleum ether and then drying it.

[0030] On the other hand, the autothermal reforming reaction catalyst 62c in the autothermal reforming reaction column 5c can be reduced by introducing hydrogen from the hydrogen cylinder 15 through the pipe 16, the mass flow controller 26, and the valve 17c into the autothermal reforming reaction column 5c, which has been heated to a set temperature by the heat source 4c. At this time, the unreacted hydrogen and the moisture produced by the reduction are released outside the system by opening the valve 14c.

[0031] In this way, by controlling the opening and closing of valves 3a, 3b, and 3c, the autothermal reforming reaction, the combustion removal of oil and tar, and the activation of the autothermal reforming reaction catalyst by hydrogen reduction are carried out in one of the autothermal reforming reaction columns 5a, 5b, and 5c. This enables continuous reformed gas generation. Furthermore, these parallel operations can be automated using programmable control. This allows for individual control while constantly repeating the operation column, combustion removal column, and activation column, making fully automated continuous operation possible.

[0032] In parallel operation, there are no particular limitations on the timing for switching between the autothermal reforming reaction in the autothermal reforming reaction columns 5a, 5b, and 5c, the combustion and removal of oil and tar, and the activation of the autothermal reforming reaction catalyst by hydrogen reduction. For example, by setting actual criteria, such as when the gas conversion rate in the autothermal reforming reaction falls below a specified value or by switching every certain operating time, the amount of high-purity methane gas can be increased.

[0033] (Type of oil supplied to autothermal reforming reaction) The oil component supplied to the autothermal reforming reaction is preferably rapeseed oil, palm oil, soybean oil, rice bran oil, sesame oil, sunflower oil, corn oil, cottonseed oil, olive oil, safflower oil, perilla oil, linseed oil, castor oil, beef tallow, lard, chicken oil, mutton tallow, milk fat, mineral oil, petrolatum, paraffin, or liquid paraffin; more preferably rapeseed oil, palm oil, soybean oil, rice bran oil, sesame oil, sunflower oil, corn oil, cottonseed oil, olive oil, safflower oil, perilla oil, linseed oil, castor oil, beef tallow, lard, chicken oil, mutton tallow, or milk fat; and most preferably rapeseed oil, palm oil, soybean oil, rice bran oil, sesame oil, sunflower oil, corn oil, cottonseed oil, olive oil, safflower oil, perilla oil, linseed oil, or castor oil. Rapeseed oil, palm oil, soybean oil, rice oil, sesame oil, sunflower oil, corn oil, cottonseed oil, olive oil, safflower oil, perilla oil, linseed oil, and castor oil are vegetable oils that are liquid at room temperature, making them easy to supply to the autothermal reforming reactor, and they do not solidify in the gas-liquid separation section even in low-temperature environments, making them less likely to clog pipes. These oils do not have to be fresh; actually used waste oil can also be used, and by building a system to collect waste tempura oil from households and using it as a raw material, it is possible to contribute to the SDGs through recycled fuel.

[0034] (oil and water supply) Regarding the amounts of oil and water supplied during the autothermal reforming reaction, the ratio of the amount of carbon contained in the oil to the amount of water (hereinafter referred to as the steam / carbon (S / C) ratio) is preferably 2 to 7, more preferably 3 to 6, and most preferably 4.5 to 5.5. If the S / C ratio is less than 2, carbon may be more likely to deposit on the catalyst, reducing activity and raising concerns that the autothermal reforming reaction may not proceed sufficiently. On the other hand, if the S / C ratio is greater than 7, there is a concern that a large amount of energy may be required to supply reaction heat, and there is no change in reaction efficiency or catalyst life, making it of little technical significance.

[0035] (Autothermal reforming reaction temperature) The autothermal reforming reaction temperature is preferably 450°C or higher and 900°C or lower, more preferably 500°C or higher and 800°C or lower, and most preferably 600°C or higher and 700°C or lower. If the reaction temperature is lower than 450°C, the oil gas conversion rate will be low, and there is a concern that the amounts of carbon monoxide and hydrogen produced will be insufficient. Also, if the temperature is higher than 900°C, no significant change in the gas conversion rate will be seen, and the technical significance will be diminished.

[0036] (Type of heat source) The heat source that supplies heat during the autothermal reforming reaction can be any of the following: electric furnace, gas burner, diesel burner, kerosene burner, heavy oil burner, and solid fuel burner. However, electric furnaces are the most preferable because they allow for more precise temperature control and are easy to handle. However, in order to make the process viable as an industry, fuels other than electric furnaces may be used to reduce fuel costs.

[0037] (Types of autothermal reforming catalysts) Any industrially used autothermal reforming catalyst can be used in the autothermal reforming reaction of the oil component of the present invention. Specifically, platinum catalysts, palladium catalysts, ruthenium catalysts, rhodium catalysts, iridium catalysts, and nickel catalysts can be preferably used.

[0038] (Autothermal reforming catalyst support) The type of catalyst carrier is not particularly limited, but silica and alumina are preferred because they have excellent durability and relatively large specific surface areas. For example, a cylindrical alumina carrier with an outer diameter of 3 mm and a length of 3 mm is used, and the catalyst described above is supported on the outer surface.

[0039] (alumina ball diameter) The diameter of the alumina balls installed inside the autothermal reforming reactor and methanation reactor is preferably 1 mm to 5 mm, more preferably 2 mm to 4 mm, and most preferably 2.5 mm to 3.5 mm. If the diameter is smaller than 1 mm, it may hinder the passage of gas inside the autothermal reforming reactor, raising concerns about an increase in internal pressure. Furthermore, if the diameter is larger than 5 mm, there is a concern that the evaporation rate of oil and water may vary depending on the location inside the autothermal reforming reactor, causing the reaction to proceed unevenly.

[0040] (Gas hourly space velocity in autothermal reforming reaction) The gas hourly space velocity (GHSV) in the autothermal reforming reaction is 5000 h -1 More than ~9200h -1 Less than 6200h is preferable -1 Over 8000h -1 Less than 6900h is preferable. -1 More than ~7300h -1 The following is most preferable: GHSV 5000h -1 If the temperature is lower than this, the amount of carbon monoxide and hydrogen produced will be small, and the practical significance will be diminished. -1 If the amount is greater than this, the gas conversion rate will be low and the amount of unreacted oil will be large, which may result in an excessive amount of waste liquid to be treated.

[0041] (ratio of oil-derived carbon to introduced oxygen) In the autothermal reforming reaction of oil, when the oil is decomposed into smaller molecules using oxygen before contacting the catalyst 62, the ratio of the amount of carbon derived from the oil to the amount of introduced oxygen (hereinafter referred to as O / C ratio) is preferably 0.1 to 1.2, more preferably 0.3 to 0.9, and most preferably 0.5 to 0.7. This is because if the O / C ratio is less than 0.1, the thermal decomposition of the oil will be insufficient, raising concerns about a decrease in gas conversion rate and an increase in tar, and if it is more than 1.2, there is a concern that the introduced oxygen will significantly reduce the activity of the catalyst 62.

[0042] (Temperature of gas-liquid separation section 10) 1, the temperature of the gas-liquid separation section 10 is preferably 0°C or higher and 30°C or lower, more preferably 0°C or higher and 15°C or lower, and most preferably 0°C or higher and 5°C or lower. If the temperature of the gas-liquid separation section 10 is lower than 0°C, the water contained in the reformed gas will turn to ice, making it difficult to remove the water from the valve 14. If the temperature is higher than 30°C, the saturated vapor pressure will increase, resulting in a decrease in the reaction efficiency in the subsequent methanation step and an increase in the amount of water vapor in the carbon dioxide removal step and the water vapor removal step. In particular, the amount of moisture absorbent that must be removed in the water vapor removal step will increase.

[0043] (Type of oil absorbent) Any material that can absorb oil and tar can be preferably used as the material for the oil absorbent 13 installed in the gas-liquid separation section 10, but polybutylene terephthalate, polyethylene, polypropylene, and polystyrene are preferred, and polyethylene, polypropylene, and polystyrene are more preferred because these have a high affinity with oil and tar but a low affinity with water.

[0044] (Shape of oil absorbent material) The shape of the oil absorbent 13 is preferably cotton, nonwoven fabric, felt, woven fabric, or knitted fabric, more preferably cotton, nonwoven fabric, or felt, and most preferably cotton, because the cotton-like oil absorbent is less likely to clog with unreacted oil or tar that has entered the gas-liquid separation section 7.

[0045] (Outline of the methanation process) In Figure 1, the reformed gas generated in the autothermal reforming reaction step is introduced from pipe 12 through valve 18 into methanation tube 20, which has been heated to a temperature range described below by heat source 19. Alumina balls 211, methanation catalyst 212, and alumina balls 213 are installed in this order inside methanation tube 20, and the hydrogen in the reformed gas reacts with carbon monoxide, carbon dioxide, and hydrogen supplied from hydrogen cylinder 15 to be converted into methane.

[0046] Thereafter, the water produced by methanation is condensed in the gas-liquid separation section 22. As a result, methane, unreacted carbon dioxide, and water vapor equivalent to the saturated water vapor pressure at the temperature of the gas-liquid separation section 22 are transferred via valve 23 and pipe 24 to the carbon dioxide removal and water vapor removal section, which is the next process.

[0047] During methanation, carbon is expected to deposit on the catalyst due to the Buder reaction (2CO → CO2 + C). For this reason, after methanation, valve 23 is closed, valve 25 is opened, and the temperature inside methanation tube 20 is raised to 500°C using heat source 19. Furthermore, valve 27 is opened to supply hydrogen from hydrogen cylinder 15 to methanation tube 20, which makes it possible to remove the carbon deposited on the catalyst and activate the catalyst.

[0048] In actual operation, as shown in FIG. 3, by installing at least two methanation tubes, such as methanation tube 20a and methanation tube 20b, one methanation tube operating for methanation and the other methanation tube removing and reactivating carbon deposited on the methanation catalyst can be performed in parallel.

[0049] That is, for example, when the reformed gas is supplied via pipe 12 and valve 18a to methanation column 20a, which has been heated to a temperature suitable for methanation by heat source 19a, and an autothermal reforming reaction is taking place, valve 18b is closed. The reformed gas produced in methanation column 20a enters gas-liquid separation section 22a and moves via valve 23a and pipe 24 to carbon dioxide removal column 29a and water vapor removal column 32a, which are the next steps. At this time, valves 25a and 23b of gas-liquid separators 22a and 22b, respectively, are closed.

[0050] Meanwhile, hydrogen is introduced from hydrogen cylinder 15 through piping 16, mass flow controller 26, and valve 27b into methanation column 20b, which has been heated to, for example, 400°C by heat source 19b. Carbon adhering to alumina balls 211b, methanation catalyst 212b, and alumina balls 213b in methanation column 20b is converted to methane, and methanation catalyst 212b is activated. Unreacted hydrogen and generated methane are discharged into gas-liquid separator 22b. By leaving valve 25b open, unreacted hydrogen and generated methane can be released outside the system through valve 25b and accumulated in other containers or facilities. This allows for planned processing.

[0051] In this way, by controlling the opening and closing of the gas-liquid separator 22a and the gas-liquid separation section 22b, the carbon attached to the wall surface inside the methanation tube and to the methanation catalyst can be burned and removed, and activation of the methanation catalyst by hydrogen reduction can be performed in either the methanation tube 20a or the methanation tube 20b.

[0052] (methanation temperature) The methanation temperature is preferably 350°C or higher and 450°C or lower, more preferably 380°C or higher and 420°C or lower, and most preferably 390°C or higher and 410°C or lower. If the reaction temperature is lower than 350°C, methanation will not proceed sufficiently, resulting in a large proportion of unreacted carbon monoxide, carbon dioxide, and hydrogen in the methanation step, which may cause a decrease in methane purity after the subsequent steam removal step and carbon dioxide removal step. Also, if the temperature is higher than 450°C, steam reforming of methane will proceed, which may cause a decrease in methane purity after the subsequent steam removal step and carbon dioxide removal step.

[0053] (Methanation heat source) The heat source that supplies heat during the autothermal reforming reaction can be any of the following: electric furnace, gas burner, diesel burner, kerosene burner, heavy oil burner, and solid fuel burner. However, electric furnaces are the most preferable because they allow for more precise temperature control and are easy to handle. However, in order to make the process viable as an industry, fuels other than electric furnaces may be used to reduce fuel costs.

[0054] (Type of methanation catalyst) Any methanation catalyst that is industrially used can be preferably used in the present invention. Specifically, ruthenium catalysts and nickel catalysts are preferably used. The type of catalyst support is not particularly limited, but silica and alumina are preferred because they have excellent durability and are commercially available with relatively large specific surface areas. For example, the support is spherical silica with a rectangular shape of 3 mm, with the above-mentioned catalyst supported on its outer surface.

[0055] (GHSV in the methanation process) The gas hourly space velocity (GHSV) of hydrogen in the methanation process is 800 h -1 Over 5000h -1 Less than 1000h is preferable. -1 Over 4000h -1 Less than 1600h is preferable. -1 More than ~2700h -1 The following is most preferable: GHSV 800h -1 If the temperature is lower than this, the amount of methane produced will be small, and the practical significance will be diminished. -1 If the amount is larger, the proportion of unreacted hydrogen will be large, which may cause a decrease in the purity of methane after the subsequent carbon dioxide removal step and water vapor removal step.

[0056] (Outline of the carbon dioxide removal process) In FIG. 1, a mixed gas of methane, carbon dioxide, and water vapor is introduced into the carbon dioxide removal column 29 through the valve 28 from the pipe 24, and is passed through and contacted with the carbon dioxide removing material 30, whereby the carbon dioxide is removed.

[0057] (Type of carbon dioxide removal material) The carbon dioxide removing material introduced into the carbon dioxide removing column 29 is preferably sodium hydroxide, potassium hydroxide, calcium hydroxide, or calcium oxide, and more preferably sodium hydroxide or potassium hydroxide.

[0058] (Carbon dioxide removal material using sodium hydroxide and potassium hydroxide) When the above-mentioned sodium hydroxide and potassium hydroxide are used to absorb carbon dioxide, it is preferable to support them on a high-specific surface area carrier, which is expected to result in high dispersion of sodium hydroxide and potassium hydroxide and an improved carbon dioxide removal rate.

[0059] (Type of carrier) Alumina, activated carbon, titanium dioxide, magnesium oxide, zirconium oxide, and cerium oxide can be used as carriers for supporting sodium hydroxide and potassium hydroxide, with alumina and activated carbon being more preferred, and activated carbon being the most preferred. Activated carbon has excellent alkali resistance and a specific surface area of ​​1000 m 2 For example, the carrier is a cylindrical alumina carrier with an outer diameter of 3 mm and a length of 3 mm, and the catalyst described above is supported on the outer surface.

[0060] (Amount of sodium hydroxide or potassium hydroxide supported on activated carbon) When the carrier is activated carbon, it is preferable that the specific surface area of ​​the activated carbon and the amount of sodium hydroxide or potassium hydroxide supported satisfy the following formula.

[0061]

number

[0062] In the above formula, M represents the amount of sodium hydroxide or potassium hydroxide supported on the carrier (mol / kg), and S represents the specific surface area of ​​the carrier (m 2 / g).

[0063] M / S is 2 x 10 ―3 If the M / S is less than 6 × 10, the amount of sodium hydroxide or potassium hydroxide supported is too small, and they are preferentially supported in the micropore region of the activated carbon, so the proportion that can contribute to carbon dioxide absorption is low, and there is a concern that carbon dioxide in the mixed gas cannot be sufficiently removed. ―3 If the size is larger, the dispersion of sodium hydroxide or potassium hydroxide will decrease, so the proportion that can contribute to the absorption of carbon dioxide will be low, and there is a concern that carbon dioxide in the mixed gas will not be sufficiently removed.

[0064] (Amount of sodium hydroxide or potassium hydroxide supported on alumina) When the carrier is alumina, it is preferable that the specific surface area of ​​the alumina and the amount of sodium hydroxide or potassium hydroxide supported satisfy the following formula.

[0065]

number

[0066] M / S is 7 x 10 ―3 If the M / S is less than 35 × 10, the amount of sodium hydroxide or potassium hydroxide supported is small, and since it is preferentially supported in the alumina micropore region, the proportion that can contribute to carbon dioxide absorption is low, and there is a concern that carbon dioxide in the mixed gas cannot be sufficiently removed. ―3 If the size is larger, the dispersion of sodium hydroxide or potassium hydroxide will decrease, so the proportion that can contribute to the absorption of carbon dioxide will be low, and there is a concern that carbon dioxide in the mixed gas will not be sufficiently removed.

[0067] (Carbon dioxide removal material consisting of calcium hydroxide and calcium oxide) When calcium hydroxide or calcium oxide is used as a carbon dioxide removal material, its specific surface area is 30m 2 / g or more. 2If the specific surface area is less than 1 / g, the frequency of contact with carbon dioxide is low, and there is a concern that carbon dioxide may not be sufficiently removed. Calcium hydroxide or calcium oxide can also be used by supporting it on a high specific surface area carrier such as alumina or activated carbon.

[0068] (Temperature inside the carbon dioxide removal tube) During the carbon dioxide removal step and the water vapor removal step, the temperature of carbon dioxide removal column 27 is preferably 0°C or higher and 50°C or lower, more preferably 10°C or higher and 35°C or lower, and most preferably 20°C or higher and 30°C or lower. If the temperature of carbon dioxide removal column 27 is lower than 0°C, moisture may condense and clog carbon dioxide removal column 27 or piping 28, and if the temperature is higher than 50°C, there is a concern that the carbon dioxide removal efficiency may decrease.

[0069] (Recycling of carbon dioxide removal materials consisting of calcium hydroxide and calcium oxide) Furthermore, when calcium hydroxide or calcium oxide is used for the carbon dioxide removal material 30, the calcium hydroxide or calcium oxide becomes calcium carbonate by absorbing carbon dioxide. Therefore, after the carbon dioxide removal material 30 absorbs carbon dioxide, valve 34 is closed, valve 39 is opened, and the material is heated to 700°C or higher with heat source 38, whereby the carbon dioxide removal material 30 can be regenerated by a decarbonation reaction (Ca(CO3)2 → CaO + CO2). Furthermore, during the decarbonation reaction, valve 37 is opened to introduce oxygen from oxygen cylinder 7 into carbon dioxide removal column 29 through piping 36, thereby burning and removing unreacted oil and tar components that have leaked from methanation column 20 and adhered to the carbon dioxide removal material 30.

[0070] (Overview of the water vapor removal process) After the carbon dioxide removal process, the gas consisting mainly of methane and water vapor is introduced into the water vapor removal column 32 through pipe 31, and the water vapor is removed by the moisture absorbent 33 inside the water vapor removal column 32. As a result, high-purity methane gas can be obtained from pipe 35 through valve 34.

[0071] (Type of moisture absorbent material) The moisture absorbent is preferably silica gel, activated carbon, calcium chloride, bentonite, or synthetic zeolite, more preferably silica gel or bentonite, and most preferably silica gel, because silica gel has a highly hydrophilic surface and is less corrosive, so there is little risk of deterioration of metal piping.

[0072] In the actual carbon dioxide removal process and water vapor removal process, by installing at least two sets of carbon dioxide removal columns and water vapor removal columns, such as carbon dioxide removal column 29a, carbon dioxide removal column 29b, water vapor removal column 32a, and water vapor removal column 32b, as shown in Figure 4, it is possible to remove carbon dioxide and water vapor from the mixed gas of carbon dioxide, methane, and water vapor sent from the methanation process, decarbonate carbon dioxide removal material 30 that has absorbed carbon dioxide, and remove moisture from moisture absorbent material 33 in parallel.

[0073] That is, for example, while the carbon dioxide removal process and the water vapor removal process are being carried out by carbon dioxide removal material 30a in carbon dioxide tube 29a and moisture absorbent material 33a in moisture vapor removal tube 32a through piping 24 and valve 28a, valves 28b, 37a, and 39a are closed, and valves 37b and 39b are opened to supply oxygen from oxygen cylinder 7 through piping 36 to carbon dioxide tube 29b, which has been heated by heat source 38b to a temperature suitable for decarbonation, thereby performing decarbonation from carbon dioxide removal material 30b and moisture removal from moisture absorbent 33b.

[0074] If sodium hydroxide or potassium hydroxide is used as the carbon dioxide removal material 30, it absorbs not only carbon dioxide but also water vapor, eliminating the need for the moisture absorbent 33. Furthermore, since carbon dioxide is converted to sodium carbonate or potassium carbonate upon absorption, for example, the carbon dioxide removal process and the water vapor removal process are performed using the carbon dioxide removal material 30a in the carbon dioxide column 29a and the moisture absorbent 33a in the water vapor removal column 32a via the pipe 24 and valve 28a. Then, valve 28a is closed, valve 28b is opened, and the carbon dioxide, methane, and water vapor mixture from the methanation process is introduced into the carbon dioxide removal material 30b in the carbon dioxide removal column 29b. During this time, the carbon dioxide column 29a can be removed and the carbon dioxide removal material 30a can be replaced with a new one. The timing of the carbon dioxide removal material replacement is not particularly limited. For example, by setting a standard tailored to the actual operating conditions, such as switching when the methane composition after the carbon dioxide removal process falls below 60%, the level at which it can be used as a substitute for natural gas, and switching based on this standard enables continuous operation that efficiently increases the amount of high-purity methane gas.

[0075] (Size of carbon dioxide removal material and moisture absorbent material) The size of the carbon dioxide removal material and moisture absorbent material is preferably such that they pass through a sieve with a mesh size of 4 mm and a wire diameter of 1.4 mm, but not a sieve with a mesh size of 250 μm and a wire diameter of 160 μm, as specified in JIS Z8801; more preferably, they pass through a sieve with a mesh size of 2 mm and a wire diameter of 0.9 mm, but not a sieve with a mesh size of 500 μm and a wire diameter of 315 μm; and most preferably, they pass through a sieve with a mesh size of 1.4 mm and a wire diameter of 0.71 mm, but not a sieve with a mesh size of 710 μm and a wire diameter of 450 μm. Materials that pass through a sieve with a mesh size of 250 μm and a wire diameter of 160 μm are difficult to handle because they tend to scatter, and if they scatter and get into the connections of valves, piping, carbon dioxide removal tube 29, water vapor removal tube 32, etc., they may cause equipment failure. On the other hand, if the particles are too small to pass through a sieve with a mesh size of 4 mm and a wire diameter of 1.4 mm, they will come into contact with carbon dioxide and water vapor less frequently, and there is a concern that these will not be sufficiently removed.

[0076] (Compression pressure and compression time in press molding of carbon dioxide removal material and moisture absorbent material) The molding pressure during the above-mentioned pressure molding is preferably 5 MPa or more and 60 MPa or less. It is more preferably 25 MPa or more and 50 MPa or less, and most preferably 35 MPa or more and 45 MPa or less. If the molding pressure is lower than 5 MPa, the compressive strength of the carbon dioxide removing material and moisture absorbent material is low, and they may easily lose their shape. If the molding pressure exceeds 60 MPa, the void volume of the carbon dioxide removing material and moisture absorbent material decreases, which may impair their ability to absorb carbon dioxide and water vapor.

[0077] The holding time for the pressure molding is preferably 1 minute to 6 minutes, more preferably 2 minutes to 5 minutes, and most preferably 3 minutes to 4 minutes. A holding time of less than 1 minute will not ensure sufficient molding, and a holding time of more than 6 minutes is of little industrial significance. (Temperature inside the water vapor removal tube) The temperature of the water vapor removal column 30 is preferably 0°C or higher and 30°C or lower, more preferably 0°C or higher and 15°C or lower, and most preferably 0°C or higher and 5°C or lower. If the temperature of the gas-liquid separation section 1 and the gas-liquid separation section 5 is lower than 0°C, there is a concern that water may condense and block the downstream piping, and if the temperature is higher than 30°C, there is a concern that the water vapor adsorbed on the moisture absorbent material may be easily desorbed, resulting in insufficient removal of the water vapor.

[0078] Examples of obtaining high-purity methane gas from oil and water will be described in detail below. Note that the examples are intended to specifically explain the invention and should not be construed as limiting the scope of the invention. Example 1

[0079] (Autothermal reforming reaction process) Oil (canola oil manufactured by Nisshin Oillio Group) was introduced into the autothermal reforming reactor 5 at a rate of 27 ml / h using the liquid feed pump 1a, and water was introduced into the autothermal reforming reactor 5 at a rate of 135 ml / h using the liquid feed pump 1b. The S / C ratio at this time was 4.8. The autothermal reforming catalyst 62 in the autothermal reforming reactor 5 was made of high specific surface area alumina (Al2O3, N-612N, manufactured by JGC Catalysts and Chemicals Co., Ltd., specific surface area: 190 m 2 A catalyst in which ruthenium was supported on Al2O3 (hereinafter referred to as Ru / Al2O3) at a concentration of 5 wt.% was used. -1 Furthermore, oxygen from an oxygen cylinder 7 was introduced into the autothermal reforming reactor 5 at a flow rate of 180 ml / min using a mass flow controller 9. This adjusted the O / C ratio to 0.6.

[0080] Regarding the conditions for the autothermal reforming reaction, the inside of the autothermal reforming reactor 5 was heated to 650°C using an electric furnace (Chudenki Co., Ltd., GSS-0710-5) as the heat source 4. The reaction product gas, tar, unreacted oil, and water-gas-liquid discharged from the autothermal reforming reactor 5 entered the separation section 10. The gas components passed through valve 11 and were transferred to piping 12, and the tar and unreacted oil were trapped in an oil absorbent 13 installed in the gas-liquid separation section 10. In this example, polyethylene wool (Tokyo Bouon Co., Ltd., sound-absorbing and heat-insulating material ESW430500) was used as the oil absorbent.

[0081] The gas discharged from pipe 12 was analyzed using a gas chromatograph with a thermal conductivity detector (hereinafter referred to as TCD-GC), and the composition of the gas was found to be 45%, 12%, 3%, and 40% hydrogen, carbon monoxide, methane, and carbon dioxide, respectively. The gas conversion rate was 81%.

[0082] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The autothermal reforming reaction causes tar, unreacted oil, and water to adhere to the alumina balls 61, the autothermal reforming catalyst 62, and the alumina balls 63. Therefore, to remove the tar, unreacted oil, and water after the autothermal reforming reaction, the temperature inside the autothermal reforming reactor 5 was maintained at 650°C, valve 3 was closed, and oxygen was circulated from the oxygen cylinder 7 into the steam reactor 5 at a flow rate of 1,000 ml / h for 2 hours. The alumina balls 61, the autothermal reforming catalyst 62, and the alumina balls 63 were then heated to 900°C at a rate of 10°C / min in an air atmosphere and thermogravimetric measurements were performed. Almost no weight loss was observed at 900°C, and visual observation of the alumina balls 61 and 63 revealed no adhesion of tar, oil, or water. Based on these findings, it is believed that the tar, unreacted oil, and water were successfully removed by circulating air while heating.

[0083] (Methanation process) The gas discharged from the pipe 12 passed through a valve 18 and was introduced into a methanation column 20 that had been preheated to 400°C by a heat source 19. At this time, the catalyst 212 contained high-specific surface area silica (SiO, silica gel Q10, manufactured by Fuji Silysia, specific surface area: 380 m 2 A catalyst (hereinafter referred to as Ru / SiO2) in which ruthenium was supported at 5 wt.% on SiO2 (0.15 wt. / g) was used to measure the GHSV of hydrogen at 2536 h. -1 It was set up so that

[0084] In the methanation column 20, carbon monoxide, carbon dioxide and hydrogen react to be converted into methane. When the gas passed through the valve 23 and exited the pipe 24 was analyzed using TCD-GC, the composition of the gas was found to be 8%, 0%, 58% and 32% hydrogen, 0%, 58% and 32%, respectively.

[0085] (Carbon dioxide removal process and water vapor removal process) The mixed gas of methane, carbon dioxide, and water vapor prepared in the methanation step was introduced through pipe 24 and valve 28 into carbon dioxide removal column 29 filled with carbon dioxide removal material 30. At this time, valve 34 was open, and valve 39 was closed.

[0086] In this embodiment, the carbon dioxide removal material 30 is activated carbon (Futamura Chemical Co., Ltd. granular carbon, HC-30E, specific surface area: 1190 m 2 / g) was used as a carrier, and 5 mmol of sodium hydroxide was supported per 1 g of the carrier. In this case, the value obtained by dividing the amount of sodium hydroxide supported in equation 1 by the specific surface area of ​​the carrier was 4.2 × 10 ―3 Furthermore, the gas components discharged from the carbon dioxide removal column 29 were introduced through a pipe 31 into a water vapor removal column 32 filled with a moisture absorbent 33. In this example, the moisture absorbent 33 was silica gel (Fuji Silysia Q10, specific surface area: 300 to 400 m 2 / g) was used. As a result, the sodium hydroxide absorbs carbon dioxide, and the silica gel removes water vapor, and a dried mixed gas with high methane purity is discharged from valve 34. Note that if the methane purity of the gas discharged from valve 34 is 60% or higher, it is considered usable as a substitute for natural gas, and was therefore deemed suitable.

[0087] The gas exiting the valve 34 was subjected to a gas composition analysis using TCD-GC, and it was found that the methane content of the exit gas was 87%.

[0088] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 2

[0089] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 46%, 11%, 3%, and 40%, respectively. The gas conversion rate was 81%.

[0090] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0091] (Methanation process) The gas was passed through the methanation step under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 8%, 1%, 53%, and 38%, respectively.

[0092] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removing material 30 used was the same activated carbon as used in Example 1, with 1.5 mmol of sodium hydroxide supported per 1 g of the carrier. In this case, the value obtained by dividing the amount of sodium hydroxide supported in equation 1 by the specific surface area of ​​the single substance was 1.3 × 10 ―3 The water vapor removal step was carried out under the same conditions as in Example 1. Thereafter, the gas exiting the valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane content of the exit gas was 74%.

[0093] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 3

[0094] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 45%, 12%, 3%, and 40%, respectively. The gas conversion rate was 80%.

[0095] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0096] (Methanation process) The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 9%, 1%, 51%, and 39%, respectively.

[0097] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removing material 30 used was the same activated carbon as used in Example 1, with 3 mmol of sodium hydroxide supported per 1 g of the carrier. In this case, the value obtained by dividing the amount of sodium hydroxide supported in equation 1 by the specific surface area of ​​the single substance was 2.5 × 10 ―3 The water vapor removal step was carried out under the same conditions as in Example 1. Thereafter, the gas exiting the valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane content of the exit gas was 80%.

[0098] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 4

[0099] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 47%, 12%, 2%, and 39%, respectively. The gas conversion rate was 81%.

[0100] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0101] (Methanation process) The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 9%, 0%, 54%, and 37%, respectively.

[0102] (Carbon dioxide removal process and water vapor removal process) In this example, activated carbon was used as the carrier for the carbon dioxide removing material 30, and 6 mmol of sodium hydroxide was supported per 1 g of the carrier. In this case, the value obtained by dividing the amount of sodium hydroxide supported in equation 1 by the specific surface area of ​​the single substance was 5.0 × 10 ―3 The water vapor removal step was carried out under the same conditions as in Example 1. Thereafter, the gas exiting the valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane content of the exit gas was 85%.

[0103] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 5

[0104] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 46%, 11%, 1%, and 42%, respectively. The gas conversion rate was 81%.

[0105] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0106] (Methanation process) The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 7%, 0%, 53%, and 38%, respectively.

[0107] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removing material 30 used was the same activated carbon as used in Example 1, with 7.5 mmol of sodium hydroxide supported per 1 g of the carrier. In this case, the value obtained by dividing the amount of sodium hydroxide supported in equation 1 by the specific surface area of ​​the single substance was 6.3 × 10 ―3 The water vapor removal step was carried out under the same conditions as in Example 1. Thereafter, the gas exiting the valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane content of the exit gas was 78%.

[0108] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 6

[0109] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 45%, 11%, 2%, and 42%, respectively. The gas conversion rate was 79%.

[0110] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0111] (Methanation process) The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 7%, 0%, 55%, and 38%, respectively.

[0112] (Carbon dioxide removal process and water vapor removal process) In this example, activated carbon was used as the carrier for the carbon dioxide removing material 30, and potassium hydroxide was supported at 5 mmol per 1 g of the carrier. In this case, the value obtained by dividing the amount of potassium hydroxide supported in Equation 2 by the specific surface area of ​​the single substance was 4.2 × 10 ―3 The water vapor removal step was carried out under the same conditions as in Example 1. Thereafter, the gas exiting the valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane content of the exit gas was 75%.

[0113] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 7

[0114] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 46%, 10%, 2%, and 42%, respectively. The gas conversion rate was 80%.

[0115] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0116] (Methanation process) The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the hydrogen, carbon monoxide, methane, and carbon dioxide compositions of the gas discharged from pipe 24 were 8%, 0%, 55%, and 37%, respectively.

[0117] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removing material 30 used was the same activated carbon as used in Example 1, with 6 mmol of potassium hydroxide supported per 1 g of the carrier. In this case, the value obtained by dividing the amount of potassium hydroxide supported in Equation 2 by the specific surface area of ​​the single substance was 5.0 × 10 ―3 The water vapor removal step was carried out under the same conditions as in Example 1. Thereafter, the gas exiting the valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane content of the exit gas was 71%.

[0118] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 8

[0119] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 46%, 11%, 3%, and 40%, respectively. The gas conversion rate was 79%.

[0120] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0121] (Methanation process) The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the hydrogen, carbon monoxide, methane, and carbon dioxide compositions of the gas discharged from pipe 24 were 8%, 0%, 53%, and 38%, respectively.

[0122] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removing material 30 used was an alumina carrier carrying 3.6 mmol of sodium hydroxide per 1 g of carrier. In this case, the value obtained by dividing the amount of sodium hydroxide carried in the equation (2) by the specific surface area of ​​the single substance was 19×10 ―3 The water vapor removal step was carried out under the same conditions as in Example 1. Thereafter, the gas exiting the valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane content of the exit gas was 74%.

[0123] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 9

[0124] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 45%, 12%, 2%, and 41%, respectively. The gas conversion rate was 81%.

[0125] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0126] (Methanation process) In this example, the GHSV of hydrogen for Ru / SiO2 is 790 h -1 The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the hydrogen, carbon monoxide, methane, and carbon dioxide compositions of the gas discharged from pipe 24 were 3%, 0%, 45%, and 48%, respectively.

[0127] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removal step and the water vapor removal step were carried out under the same conditions as in Example 1. After that, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition in the outlet gas was 82%.

[0128] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 10

[0129] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 44%, 13%, 3%, and 40%, respectively. The gas conversion rate was 80%.

[0130] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0131] (Methanation process) In this example, the GHSV of hydrogen for Ru / SiO2 is 1580 h -1 The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 6%, 0%, 49%, and 43%, respectively.

[0132] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removal step and the water vapor removal step were carried out under the same conditions as in Example 1. After that, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition in the outlet gas was 74%.

[0133] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 11

[0134] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 45%, 12%, 4%, and 39%, respectively. The gas conversion rate was 82%.

[0135] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0136] (Methanation process) In this example, the GHSV of hydrogen for Ru / SiO2 is 2287 h -1 The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 7%, 0%, 50%, and 42%, respectively.

[0137] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removal step and the water vapor removal step were carried out under the same conditions as in Example 1. After that, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition in the outlet gas was 82%.

[0138] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 12

[0139] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 44%, 12%, 3%, and 41%, respectively. The gas conversion rate was 80%.

[0140] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0141] (Methanation process) In this example, the GHSV of hydrogen for Ru / SiO2 is 2744 h -1 The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 12%, 0%, 55%, and 30%, respectively.

[0142] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removal step and the water vapor removal step were carried out under the same conditions as in Example 1. After that, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition accounted for 75% of the outlet gas.

[0143] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 13

[0144] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 45%, 12%, 3%, and 40%, respectively. The gas conversion rate was 81%.

[0145] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0146] (Methanation process) In this example, the GHSV of hydrogen for Ru / SiO2 is 3992 h -1 The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 32%, 0%, 52%, and 16%, respectively.

[0147] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removal step and the water vapor removal step were carried out under the same conditions as in Example 1. After that, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition in the outlet gas was 61%.

[0148] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and steam removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was deemed appropriate, and a description thereof will be omitted. Example 14

[0149] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 47%, 12%, 3%, and 38%, respectively. The gas conversion rate was 80%.

[0150] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1.

[0151] (Methanation process) In this example, the methanation tube temperature was set to 350°C, and the methanation step was carried out under other conditions similar to those of Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 18%, 1%, 44%, and 36%, respectively.

[0152] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removal step and the water vapor removal step were carried out under the same conditions as in Example 1. After that, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition in the outlet gas was 62%.

[0153] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 15

[0154] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 45%, 11%, 3%, and 41%, respectively. The gas conversion rate was 79%.

[0155] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0156] (Methanation process) In this example, the methanation tube temperature was set to 380°C, and the methanation step was carried out under other conditions similar to those of Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 13%, 0%, 45%, and 41%, respectively.

[0157] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removal step and the water vapor removal step were carried out under the same conditions as in Example 1. After that, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition accounted for 75% of the outlet gas.

[0158] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 16

[0159] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 45%, 12%, 3%, and 40%, respectively. The gas conversion rate was 78%.

[0160] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0161] (Methanation process) In this example, the methanation tube temperature was set to 420°C, and the methanation process was carried out under other conditions similar to those of Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the hydrogen, carbon monoxide, methane, and carbon dioxide compositions of the gas discharged from pipe 24 were 11%, 0%, 48%, and 40%, respectively.

[0162] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removal step and the water vapor removal step were carried out under the same conditions as in Example 1. After that, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition in the outlet gas was 81%.

[0163] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process according to this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Example 17

[0164] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 45%, 12%, 2%, and 41%, respectively. The gas conversion rate was 80%.

[0165] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0166] (Methanation process) In this example, the methanation tube temperature was set to 450°C, and the methanation process was carried out under other conditions similar to those of Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the hydrogen, carbon monoxide, methane, and carbon dioxide compositions of the gas discharged from pipe 24 were 12%, 0%, 47%, and 42%, respectively.

[0167] (Carbon dioxide removal process and water vapor removal process) In this example, the carbon dioxide removal step and the water vapor removal step were carried out under the same conditions as in Example 1. After that, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition in the outlet gas was 78%.

[0168] (comprehensive evaluation) When the oil was subjected to the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process of this example, a methane-containing gas with a methane ratio of 60% or more was obtained. Therefore, the overall evaluation of this example was judged to be appropriate. Comparative Example 1

[0169] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 46%, 11%, 2%, and 41%, respectively. The gas conversion rate was 81%.

[0170] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0171] (Methanation process) The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the hydrogen, carbon monoxide, methane, and carbon dioxide compositions of the gas discharged from pipe 24 were 8%, 0%, 57%, and 34%, respectively.

[0172] (Carbon dioxide removal process and water vapor removal process) In this comparative example, no carbon dioxide removing material was used, and the carbon dioxide removing material 30 was empty. The water vapor removing step was carried out under the same conditions as in Example 1. Thereafter, the gas exiting the valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane content of the exit gas was 57%.

[0173] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation and carbon dioxide removal process, and water vapor removal process based on Comparative Example 1, the methane ratio fell below 60%. Therefore, the overall evaluation of this example was judged to be inadequate. Note that, because no carbon dioxide removal material was used in this comparative example, it was not possible to remove the carbon dioxide contained in the gas after the methanation process, which is thought to have resulted in a low methane composition in the outlet gas. Comparative Example 2

[0174] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 44%, 10%, 3%, and 43%, respectively. The gas conversion rate was 79%.

[0175] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0176] (Methanation process) The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 8%, 0%, 56%, and 35%, respectively.

[0177] (Carbon dioxide removal process and water vapor removal process) In this comparative example, the carbon dioxide removing material 30 used was the same activated carbon as used in Example 1, but with 15 mmol of sodium hydroxide supported per 1 g of the carrier. The water vapor removal step was carried out under the same conditions as in Example 1. At this time, the value obtained by dividing the amount of sodium hydroxide supported in equation 1 by the specific surface area of ​​the single substance was 12.5 x 10 ―3 This becomes: Thereafter, the gas exiting the valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane content of the exit gas was 58%.

[0178] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and water vapor removal process based on this comparative example, the methane ratio fell below 60%. This is presumably because excess sodium hydroxide blocked the pore entrances present on the activated carbon, preventing contact between the sodium hydroxide inside the pores and carbon dioxide. Therefore, the overall evaluation of this example was deemed inadequate. Comparative Example 3

[0179] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 46%, 12%, 3%, and 39%, respectively. The gas conversion rate was 79%.

[0180] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0181] (Methanation process) In Comparative Example 3, the GHSV of hydrogen for Ru / SiO2 was 5031 h -1The methanation step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 40%, 0%, 52%, and 8%, respectively.

[0182] (Carbon dioxide removal process and water vapor removal process) In this Comparative Example 3, the carbon dioxide removal step and the water vapor removal step were carried out under the same conditions as in Example 1. Thereafter, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition in the outlet gas was 56%.

[0183] (comprehensive evaluation) When the oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and steam removal process according to Comparative Example 3, the methane ratio fell below 60%. This was because the excess hydrogen supplied in the methanation process could not be consumed by methanation, and the hydrogen composition in the gas after the carbon dioxide and steam removal processes was high, resulting in a relative decrease in the methane composition. Therefore, the overall evaluation of this example was deemed inadequate. Comparative Example 4

[0184] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 45%, 11%, 4%, and 40%, respectively. The gas conversion rate was 80%.

[0185] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0186] (Methanation process) In Comparative Example 4, the methanation step was carried out without supplying hydrogen. (The GHSV of hydrogen relative to Ru / SiO2 was 0 h.)-1 ), and the other conditions were the same as in Example 1, and the methanation step was carried out, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 7%, 0%, 30%, and 62%, respectively.

[0187] (Carbon dioxide and water vapor removal process) In this Comparative Example 4, the carbon dioxide and water vapor removal process was carried out under the same conditions as in Example 1. Thereafter, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition in the outlet gas was 47%.

[0188] (comprehensive evaluation) When the oil was passed through the autothermal reforming reaction process, methanation process, carbon dioxide removal process, and steam removal process of Comparative Example 4, the methane ratio fell below 60%. This is thought to be because insufficient hydrogen was supplied to the methanation process to consume the carbon dioxide produced in the autothermal reforming reaction process. Therefore, the overall evaluation of this example was judged to be inadequate. Comparative Example 5

[0189] (Autothermal reforming reaction process) The autothermal reforming reaction step was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the compositions of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 12 were 45%, 12%, 4%, and 39%, respectively. The gas conversion rate was 81%.

[0190] (Removal of tar, unreacted oil and moisture from the autothermal reforming reactor) The experiment was carried out under the same conditions as in Example 1, so the description will be omitted.

[0191] (Methanation process) In Comparative Example 5, the temperature of the methanation column was set to 300°C, and the methanation process was carried out under the same conditions as in Example 1, and the gas components were analyzed in the same manner as in Example 1. As a result, the composition of hydrogen, carbon monoxide, methane, and carbon dioxide in the gas discharged from pipe 24 was 29%, 2%, 21%, and 46%, respectively.

[0192] (Carbon dioxide removal process and water vapor removal process) In this Comparative Example 5, the carbon dioxide removal step and the water vapor removal step were carried out under the same conditions as in Example 1. After that, the gas discharged from valve 34 was subjected to a gas composition analysis in the same manner as in Example 1, and it was found that the methane composition in the outlet gas was 41%.

[0193] (comprehensive evaluation) When oil was passed through the autothermal reforming reaction step, methanation step, carbon dioxide removal step, and water vapor removal step in accordance with Comparative Example 5, the methane ratio fell below 60%. This is thought to be because the reaction tube temperature in the methanation step was low, preventing methanation from proceeding sufficiently and resulting in insufficient methane production. Therefore, the overall evaluation of this example was deemed inadequate.

[0194] Table 1 shows the conditions for the autothermal reforming reaction process, gas-liquid separation process, methanation process, and carbon dioxide removal process carried out in Examples 1 to 17 and Comparative Examples 1 to 5 described above, and Table 2 shows the gas composition after the autothermal reforming reaction process, the gas conversion rate after the autothermal reforming reaction process, the gas composition after the methanation process, the methane composition after carbon dioxide removal, and the overall evaluation. [Table 1] [Table 2] [Explanation of symbols]

[0195] 1a, 1b Liquid transfer pump 2 Piping 3a, 3b, 3c valves 4, 4a, 4b, 4c heat source 5, 5a, 5b, 5c Autothermal reforming reactor 61, 61a, 61b Alumina balls 62, 62a, 62b, 62c Autothermal reforming catalyst 63, 63a, 63b Alumina balls 7. Oxygen Cylinder 8 Piping 9, 9a, 9b Mass flow controller 10, 10a, 10b Gas-liquid separation section 11, 11a, 11b, 11c valves 12 Piping 13, 13a, 13b Oil absorbent 14, 14a, 14b, 14c valves 15 Hydrogen Cylinder 16 Piping 17, 17a, 17b, 17c valves 18, 18a, 18b valves 19, 19a, 19b Heat source 20, 20a, 20b Methanation tube 211, 211a, 211b Alumina balls 212, 212a, 212b Methanation catalysts 213, 213a, 213b Alumina balls 22, 22a, 22b Gas-liquid separation section 23, 23a, 23b valves 24 Piping 25, 25a, 25b valves 26 Mass flow controller 27, 27a, 27b valves 28, 28a, 28b valves 29, 29a, 29b Carbon dioxide removal tube 30, 30a, 30b Carbon dioxide removal material 31 Piping 32, 32a, 32b Water vapor removal tube 33, 33a, 33b Moisture absorbing material 34 Valve 35 Piping 36 Piping 37, 37a, 37b valves 38, 38a, 38b heat source 39, 39a, 39b valves 40 Piping

Claims

1. a gas-liquid separation step in which unreacted oil contained in the reformed gas generated in the autothermal reforming reaction gas generation step is absorbed by an oil absorbent material and simultaneously condenses and separates the tar and water contained in the reformed gas generated from the reformed gas; a methanation step in which the hydrogen, carbon monoxide, and carbon dioxide contained in the reformed gas that has passed through the gas-liquid separation step are converted into methane to increase the amount of methane, while allowing the introduction of hydrogen gas for carbon removal; and a carbon dioxide removal step in which the methanation gas obtained in the methanation step is brought into contact with a carbon dioxide removal material to remove the carbon dioxide.

2. 2. The method for producing a high-purity methane-containing gas according to claim 1, wherein the carbon dioxide removing material is activated carbon that supports at least one of sodium hydroxide and potassium hydroxide so as to satisfy the following formula: [Equation 1] The above M represents the amount (mol / kg) of at least one of sodium hydroxide and potassium hydroxide supported on the carrier, and the above S represents the specific surface area (m ２ / g), respectively.

3. 2. The method for producing a high-purity methane-containing gas according to claim 1, wherein the carbon dioxide removing material comprises alumina carrying at least one of sodium hydroxide and potassium hydroxide so as to satisfy the following mathematical formula: [Equation 2] The above M represents the amount (mol / kg) of at least one of sodium hydroxide and potassium hydroxide supported on the carrier, and S represents the specific surface area (m ２ / g), respectively.

4. an autothermal reforming reactor having an alumina layer for generating steam and an autothermal reforming catalyst layer below the alumina layer, and equipped with a heat source for controlling heating to a high temperature; a raw material supply unit for supplying raw oil and water to the autothermal reforming reactor while controlling the amounts thereof; an oxygen supply unit for supplying oxygen to the autothermal reforming reactor while controlling the flow rate; a first hydrogen supply unit for supplying hydrogen to the autothermal reforming reactor while controlling the flow rate; a first gas-liquid separation unit for receiving the autothermal reforming reaction gas generated in the autothermal reforming reactor in an environment of 0°C to 30°C and delivering the reformed gas while absorbing oil and tar; and a heat source for receiving the reformed gas from the first gas-liquid separation unit and raising the temperature while controlling the internal temperature. a methanation column having a methanation catalyst layer behind an alumina layer, into which hydrogen from the first hydrogen supply source is introduced while controlling the flow rate; a second hydrogen supply unit that introduces hydrogen into the methanation column while controlling the flow rate; a second gas-liquid separation unit that receives a water-containing post-methanation gas produced in the methanation column, separates the water from the post-methanation gas components, and delivers the post-methanation gas components; and a carbon dioxide removal column that receives the water-containing post-methanation gas components from the second gas-liquid separation unit and oxygen from an oxygen source, is equipped with a heat source that controls the internal temperature within a range of 0°C to 50°C, and is filled with activated carbon.

5. 5. The high-purity methane-containing gas production apparatus according to claim 4, wherein the carbon dioxide removal column is provided with a carbon dioxide removal material in which at least one of sodium hydroxide and potassium hydroxide is supported on activated carbon so as to satisfy the following mathematical formula: [Equation 1] The above M represents the amount (mol / kg) of at least one of sodium hydroxide and potassium hydroxide supported on the carrier, and the above S represents the specific surface area (m ２ / g), respectively.

6. 5. The method for producing a high-purity methane-containing gas according to claim 4, wherein the carbon dioxide removal column is provided with a carbon dioxide removal material in which at least one of sodium hydroxide and potassium hydroxide is supported on alumina so as to satisfy the following mathematical formula: [Equation 2] The above M represents the amount (mol / kg) of at least one of sodium hydroxide and potassium hydroxide supported on the carrier, and S represents the specific surface area (m ２ / g), respectively.

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