Fuel production method and fuel production device

Abstract

The present invention efficiently produces a fuel having a high use value from plant-derived biomass. This fuel production method comprises: a thermal decomposition step for thermally decomposing plant-derived biomass at 350-430°C to obtain a gas component and a solid component; a liquefying step for cooling the gas component to obtain a liquid component; a deoxygenation treatment step for subjecting the liquid component to a deoxygenation treatment to obtain a liquid fuel; a pulverization step for pulverizing the solid component to obtain a powder; and a mixing step for mixing the powder with either one or each of a fuel oil and water to obtain a slurry fuel.

Description

Fuel production method and fuel production device

[0001] The present invention relates to a method for producing fuel using plant biomass as a raw material, and also to an apparatus for producing fuel using plant biomass as a raw material.

[0002] In order to curb global warming, efforts are being made on a global scale to reduce greenhouse gas emissions. Among these, CO2, which is derived from energy and accounts for the majority of greenhouse gas emissions, is a major cause of global warming. ２ There is an urgent need to reduce emissions.

[0003] For example, currently, jet fuel produced by refining crude oil is widely used as aviation fuel, but there is a demand to replace most of it with "sustainable aviation fuel (SAF)" derived from biomass, etc. Also, diesel and heavy oil are widely used as fuels in various engines, including industrial and marine engines, but there is a desire to replace these fuels with fuels derived from biomass.

[0004] Against this background, there has been active research into technologies for producing alternative fuels to fossil fuels from plant biomass. Plants absorb CO2 from the atmosphere during their growth process. ２ If fuel derived from plant biomass is used, CO2 in the atmosphere will be absorbed. ２ This is because the amount of carbon dioxide does not increase (carbon neutral).

[0005] One common method of utilizing plant biomass is to use charcoal obtained by burning wood and other materials as solid fuel. However, the use of this charcoal is limited because it cannot be used as aviation fuel or diesel engine fuel in its solid form.

[0006] Therefore, as described in Patent Document 1, research is being conducted into producing liquid fuel from gas components obtained by heating plant biomass.

[0007] JP 2023-156900 A

[0008] Thus, the products produced when biomass is pyrolyzed vary depending on the pyrolysis temperature. When pyrolysis is performed at high temperatures, the proportion of gaseous components increases, while at low temperatures, the solid content increases.

[0009] (1) For example, when the purpose is to produce solid fuel from biomass, pyrolysis must be carried out at a low temperature (typically about 200 to 300°C) to increase the yield of solids. Pyrolysis carried out at such a low temperature is called "torrefaction."

[0010] (2) On the other hand, when the goal is to liquefy gaseous components to produce bio-oil, it is necessary to increase the yield of the gaseous components, so pyrolysis must be carried out at a high temperature (typically around 500 to 600°C). Pyrolysis carried out at such a high temperature is called "fast pyrolysis."

[0011] (3) Another known method is to synthesize liquid hydrocarbons from hydrogen and carbon monoxide obtained by gasifying biomass using the Fischer-Tropsch (FT) process. However, this method requires pyrolysis at even higher temperatures (typically around 700 to 900°C) to decompose biomass into hydrogen and carbon monoxide.

[0012] As described in (1) to (3) above, in the past, in order to increase the yield of the target product (solid or gaseous component), it was common to pyrolyze biomass at high temperatures of 500°C or higher or low temperatures of 300°C or lower. On the other hand, when pyrolysis is carried out in the intermediate temperature range, gaseous components and solid components are obtained in similar proportions, but until now, there has been no technology to effectively utilize both as fuel.

[0013] The present inventors have conducted studies to solve the above problems and have made the following findings.

[0014] (1) By liquefying the gaseous components obtained by pyrolysis of plant biomass and then subjecting them to oxygen reduction treatment, it is possible to obtain a liquid fuel that is relatively light and has a reduced oxygen content, making it highly useful. The liquid fuel thus obtained can be further hydrorefined as necessary and then suitably used as aviation fuel, a raw material for chemical products, and the like.

[0015] (2) On the other hand, the solid component produced by the pyrolysis can be pulverized into powder and mixed with fuel oil and water to obtain a slurry fuel. The slurry fuel obtained in this manner can be suitably used as a fuel for diesel engines and gas turbine engines. In particular, the slurry fuel obtained by mixing the powder with water does not contain fossil fuel and can therefore be said to be a carbon-neutral fuel.

[0016] (3) By combining the above processes (1) and (2), the components contained in plant biomass can be utilized extremely efficiently with almost no waste.

[0017] (4) However, in order to achieve both the above processes (1) and (2) and obtain high-quality fuel, it is extremely important to control the temperature during thermal decomposition of plant biomass within a specific range of 350 to 430°C.

[0018] The present invention has been made to solve the above problems, and has the following gist and configuration.

[0019] 1. A fuel production method comprising: a pyrolysis step of pyrolyzing plant biomass at 350 to 430°C to obtain gaseous and solid components; a liquefaction step of cooling the gaseous components to obtain a liquid component; an oxygen reduction step of reducing the oxygen in the liquid component to obtain a liquid fuel; a crushing step of crushing the solid component to obtain a powder; and a mixing step of mixing the powder with fuel oil and / or water to obtain a slurry fuel.

[0020] 2. The fuel production method according to item 1, further comprising a first hydrogen production step of producing hydrogen from a first off-gas that was not liquefied in the liquefaction step.

[0021] 3. The fuel production method according to 1 or 2 above, further comprising a second hydrogen production step of producing hydrogen from a second off-gas by-produced in the oxygen reduction treatment step.

[0022] 4. The fuel production method according to any one of 1 to 3 above, wherein the powder has an average circularity of 0.5 to 1 for particles whose particle diameters in a volume-based particle size distribution are within ±10% of the average particle diameter.

[0023] 5. A fuel production system comprising: a pyrolysis device that thermally decomposes plant biomass at 350 to 430°C to obtain gaseous and solid components; a liquefaction device that cools the gaseous components to obtain a liquid component; an oxygen reduction treatment device that reduces the oxygen in the liquid component to obtain a liquid fuel; a crushing device that crushes the solid component to obtain a powder; and a mixing device that mixes the powder with fuel oil and / or water to obtain a slurry fuel.

[0024] 6. The fuel production system according to item 5 above, further comprising a first hydrogen production unit that produces hydrogen from the first off-gas that was not liquefied in the liquefaction unit.

[0025] 7. The fuel production system according to the above item 5 or 6, further comprising a second hydrogen production unit that produces hydrogen from a second off-gas by-produced in the oxygen reduction treatment unit.

[0026] According to the present invention, highly useful fuel can be produced extremely efficiently using plant biomass as a raw material.

[0027] 1 is a flow chart showing a fuel production method according to one embodiment of the present invention, and FIG. 2 is a flow chart showing a fuel production method according to another embodiment of the present invention.

[0028] Next, a method for carrying out the present invention will be specifically described.

[0029] Fig. 1 is a flow diagram showing a fuel production method according to one embodiment of the present invention. As shown in Fig. 1, the fuel production method according to this embodiment includes the following steps (1) to (5): (1) pyrolysis step, (2) liquefaction step, (3) oxygen reduction treatment step, (4) pulverization step, and (5) mixing step.

[0030] Furthermore, a fuel production apparatus according to one embodiment of the present invention includes the following (A) to (E) corresponding to the steps (1) to (5) above: (A) thermal decomposition device, (B) liquefaction device, (C) oxygen reduction treatment device, (D) pulverization device, and (E) mixing device.

[0031] Each of the above steps and devices will be described below.

[0032] [Pyrolysis Step] First, plant biomass is pyrolyzed at 350 to 430° C. to obtain gaseous and solid components (pyrolysis step).

[0033] The plant biomass is not particularly limited as long as it is an organic matter derived from a plant, and any plant biomass can be used. The plant biomass may be woody biomass, herbaceous biomass, or a mixture thereof.

[0034] Examples of woody biomass include, but are not limited to, cedar, cypress, pine, sawtooth oak, cherry, ash, zelkova, beech, oak, maple, ginkgo, paulownia, chestnut, eucalyptus, teak, mahogany, hiba, poplar, acacia, fir, birch, foxtail, walnut, sawara, kaya, yew, oak, katsura, fir, etc. Among these, it is preferable to use at least one of cedar and acacia.

[0035] Examples of herbaceous biomass include, but are not limited to, rice (straw, rice husk), wheat (straw, rice husk), buckwheat (straw, rice husk), sugarcane, Erianthus, corn, rapeseed, soybean, palm, reed, bamboo, bamboo, and sugar beet. Fruits (husks, residue after juice extraction, etc.) can also be used. Among these, it is preferable to use at least one selected from the group consisting of cedar, acacia, bamboo, sugarcane (bagasse), Erianthus, rice, wheat, buckwheat, and fruit.

[0036] The form of the plant biomass is not particularly limited, and may be in any form, such as pulverized material in the form of powder, waste, chips, bark, pomace, sawdust, or pruning residue.

[0037] The moisture content of the plant biomass to be subjected to pyrolysis is not particularly limited, but if it is too high, the efficiency of pyrolysis decreases and the amount of moisture contained in the gaseous components increases. Therefore, the moisture content of the plant biomass is preferably 50% by weight or less, and more preferably 30% by weight. On the other hand, the lower limit of the moisture content is not particularly limited and may be 0%. However, if an attempt is made to reduce the moisture content too much, the time and energy required for pre-drying will increase, resulting in a decrease in productivity. Therefore, the moisture content may be 5% by weight or more.

[0038] In order to adjust the moisture content, the plant biomass may be subjected to a drying treatment prior to the pyrolysis step. The method of the drying treatment is not particularly limited, and may be either natural drying (natural drying) or forced drying (artificial drying), or a combination thereof.

[0039] - Pyrolysis It is extremely important that the pyrolysis of plant biomass is carried out at a temperature of 350 to 430° C. The reason for this is explained below.

[0040] Plant biomass is primarily composed of the polysaccharides cellulose and hemicellulose, and lignin, a polymeric compound containing aromatic rings. In the present invention, pyrolysis is performed at a relatively low temperature of 350 to 430°C, allowing for selective pyrolysis and volatilization of cellulose and hemicellulose. On the other hand, lignin hardly undergoes pyrolysis in this temperature range and remains as a solid component. Therefore, the liquid component (pyrolysis oil) obtained by liquefying the volatilized gas components is relatively light (contains a high proportion of low-boiling-point components). Therefore, the liquid fuel finally obtained by the method of the present invention can be suitably used as aviation fuel (SAF) or as a green chemical raw material for chemical products.

[0041] Furthermore, while it is common to produce carbonized materials such as charcoal by pyrolysis of plant biomass, pyrolysis is typically performed at higher temperatures, resulting in almost no residual volatile components (oil) in the resulting carbonized material. In contrast, in the present invention, pyrolysis is performed at a low temperature of 350 to 400°C, resulting in a relatively large amount of residual oil in the resulting solid component (carbonized material). Therefore, as described below, a slurry fuel obtained by mixing the solid component with fuel oil has ignition properties comparable to those of diesel or heavy oil. Furthermore, the slurry fuel is comparable to heavy oil A in terms of lubricity and wear resistance.

[0042] For the above reasons, it is important to carry out the thermal decomposition at 350 to 430° C. From the viewpoint of enhancing the above effects, the thermal decomposition temperature is preferably 360° C. or higher, more preferably 370° C. or higher, and even more preferably 380° C. or higher. Similarly, the thermal decomposition temperature is preferably 420° C. or lower, and more preferably 410° C. or lower.

[0043] The atmosphere in which the pyrolysis is performed is not particularly limited, but the oxygen concentration in the atmosphere is preferably less than 5%, more preferably less than 3%. The oxygen concentration can be achieved, for example, by performing the pyrolysis in a furnace that is isolated from the outside air. This is because oxygen in the furnace is consumed as the pyrolysis progresses, and the furnace becomes substantially oxygen-free. Alternatively, an inert gas atmosphere with a reduced oxygen concentration can be created by supplying an inert gas into the furnace. Examples of the inert gas that can be used include nitrogen and argon. The lower limit of the oxygen concentration is also not particularly limited, but may be 0%.

[0044] The treatment time in the pyrolysis step (heating time at the above temperature) is not particularly limited, but is preferably 10 minutes or more, more preferably 15 minutes or more, and even more preferably 20 minutes or more. On the other hand, the upper limit of the treatment time is also not limited, but is preferably 120 minutes or less, more preferably 90 minutes or less, and even more preferably 80 minutes or less.

[0045] The pyrolysis apparatus for carrying out the pyrolysis is not particularly limited, and various furnaces can be used. The pyrolysis may be carried out in either a batch or continuous (flow) manner. In the case of a batch method, a box furnace, for example, can be used as the pyrolysis apparatus. In the case of a continuous method, a mesh belt type continuous firing furnace, a tunnel kiln, a rotary kiln, or the like can be suitably used as the pyrolysis apparatus.

[0046] When a batch furnace is used, the temperature rise rate is not particularly limited and heating can be performed at any rate. The temperature rise rate is, for example, preferably 1°C / min, more preferably 2°C / min or more, and even more preferably 5°C / min or more. On the other hand, the temperature rise rate is preferably 50°C / min or less, more preferably 20°C / min or less, and even more preferably 10°C / min or less.

[0047] When using a rotary kiln, the kiln length is not particularly limited, but is preferably 1 m to 100 m, more preferably 5 m to 75 m, and even more preferably 10 m to 50 m. The inner diameter of the kiln is also not particularly limited, but is preferably 0.2 m to 20 m, more preferably 0.3 m to 15 m, and even more preferably 0.5 m to 10 m. The inclination angle of the kiln is also not particularly limited, but is preferably 0.1 ° to 20 °, more preferably 0.5 ° to 15 °, and even more preferably 1.0 ° to 10 °. The rotation speed of the kiln is also not particularly limited, but is preferably 0.1 to 20 rotations per minute, more preferably 0.2 to 15 rotations, and even more preferably 0.5 to 10 rotations.

[0048] The kiln may typically be of an externally heated type. A baffle or the like may be installed on the inner surface of the kiln to promote mixing and stirring.

[0049] [Liquefaction Step] Next, the gas component generated in the thermal decomposition step is cooled to obtain a liquid component (liquefaction step).

[0050] Any liquefaction device can be used to liquefy the gaseous components without any particular limitations. For example, a scrubber can be used as the liquefaction device. In this case, the gaseous components introduced into the scrubber are cooled and liquefied by contact with the liquid components in the scrubber. The liquid components are preferably cooled by heat exchange with cooling water and circulated.

[0051] The cooling temperature in the liquefaction step is not particularly limited, and may be cooled to a temperature at which the gas components are liquefied. From the viewpoint of sufficient liquefaction, the cooling temperature is preferably 100°C or lower, more preferably 95°C or lower, preferably 40°C or lower, more preferably 35°C or lower, and even more preferably 30°C or lower. For example, cooling to ambient temperature (room temperature) may be performed. On the other hand, excessive cooling is not necessary, so the cooling temperature may be 0°C or higher, 5°C or higher, or 10°C or higher. Furthermore, when aging treatment is performed at a temperature higher than room temperature as described below, the cooling temperature is preferably 70°C or higher, more preferably 80°C or higher. By performing liquefaction at such a relatively high temperature, the energy required for heating during aging treatment can be reduced.

[0052] The composition of the liquid component obtained in the liquefaction step varies depending on the type of plant biomass used as the raw material and the pyrolysis temperature, but typically contains alcohol compounds, aldehyde compounds, ketone compounds, hydrocarbon compounds, organic acid compounds, water, etc. From the viewpoint of the usefulness of the final fuel, it is preferable that the liquid component contains a large amount of 1-hydroxy-2-propanone, for example. The content of 1-hydroxy-2-propanone in the liquid component is preferably 5% by weight to 60% by weight.

[0053] Furthermore, since the liquid component is derived from plant biomass, the sulfur content tends to be extremely low and is usually substantially free of sulfur. The sulfur content in the liquid component is, for example, 0.5 wt % or less, preferably 0.1 wt % or less. The lower limit of the sulfur content is not particularly limited, but may be 0%.

[0054] The gaseous components generated in the pyrolysis step contain mist, which may contain fine carbides and the like. If the mist continues to be processed while containing carbides and the like, the quality of the liquid fuel obtained as a result will be reduced. Therefore, from the viewpoint of improving the quality of the liquid fuel, it is preferable to remove the mist contained in the gaseous components generated in the pyrolysis step (mist removal step) prior to the liquefaction step. A cyclone-type mist separator or the like can be used to remove the mist.

[0055] [Oxygen reduction treatment process] The liquid component obtained in the above-mentioned liquefaction process has a low calorific value and is not suitable for use as fuel as it is. This is because it contains a large amount of oxygen atoms derived from the raw plant biomass in the form of carboxyl groups (-COOH) and the like. In addition, because it is highly acidic and hydrophilic, it is not compatible with general fuels and cannot be used in combination.

[0056] Therefore, the oxygen content of the liquid component is reduced by subjecting it to oxygen reduction treatment. By reducing the oxygen content, not only is the calorific value improved, but compatibility with other fuels is also improved. The liquid fuel obtained by subjecting the liquid component to oxygen reduction treatment can be used as a fuel for diesel engines, etc. Furthermore, by further subjecting the liquid component to hydrorefining treatment as necessary, it can also be suitably used as aviation fuel (SAF) or as a green chemical as a raw material for chemical products.

[0057] The method of the oxygen reduction treatment is not particularly limited, and any method can be used as long as it can reduce the oxygen content. A preferred method of the oxygen reduction treatment will be described below.

[0058] Aging Treatment The present inventors have found that the oxygen content can be reduced simply by holding the liquid component obtained in the liquefaction step under normal pressure. In this specification, the treatment of holding the liquid component under normal pressure is referred to as "aging treatment." The reduction in oxygen content due to aging treatment is thought to be due to the progress of dehydration condensation of the thermal decomposition product contained in the liquid component. This dehydration condensation reaction proceeds slowly even at room temperature and normal pressure, so heating is not essential in the aging treatment. In other words, oxygen reduction treatment can be performed simply by holding the liquid component at room temperature (ambient temperature) without heating.

[0059] However, since the rate of chemical reactions depends on temperature, a low temperature will result in a long time for the oxygen reduction treatment. Therefore, the temperature at which the aging treatment is performed (aging temperature) is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher.

[0060] Furthermore, from the viewpoint of shortening the treatment time, the aging treatment can be performed at a higher temperature. In this case, the aging temperature is not particularly limited, as long as it is a temperature higher than room temperature (ambient temperature). However, from the viewpoint of effectively shortening the treatment time, the aging temperature is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher. On the other hand, since the reaction rate increases as the temperature increases, the upper limit of the heating temperature is not particularly limited. However, typically, the aging temperature is preferably 100°C or lower, more preferably 95°C or lower, and even more preferably 90°C or lower.

[0061] When aging is performed at a temperature higher than room temperature, the liquid component can be heated as needed. Furthermore, when liquefaction is performed at a relatively high temperature, for example, around 90° C., the recovered liquid component is already at a high temperature. Therefore, the aging treatment can be performed by placing the liquid component in a tank or the like and keeping it warm.

[0062] The time for which the aging treatment is performed (treatment time) is not particularly limited and may be determined so as to obtain the desired effect. For example, when the aging treatment is performed without heating, the treatment time is preferably 50 days or more, more preferably 100 days or more, and even more preferably 150 days or more. On the other hand, if the treatment time is too long, productivity decreases. Therefore, the treatment time is preferably 600 days or less, more preferably 500 days or less, and even more preferably 400 days or less.

[0063] When the aging treatment is performed while heating, the treatment time can be shortened. Therefore, the treatment time is, for example, preferably 10 days or less, more preferably 5 days or less, and more preferably 3 days or less. On the other hand, from the viewpoint of sufficiently reducing the oxygen content, the treatment time is, for example, preferably 10 hours or more, and more preferably 24 hours or more.

[0064] Hydrothermal Treatment In another embodiment, the oxygen reduction treatment can be performed by heating and pressurizing the liquid component. This type of treatment, which involves heating and pressurization, is generally called hydrothermal treatment. The liquid component obtained by pyrolyzing plant biomass under the above conditions usually contains moisture. Therefore, in this hydrothermal treatment, heating and pressurization are performed in the presence of moisture. However, the hydrothermal treatment may be performed after adding more moisture to the liquid component.

[0065] Although the specific conditions for the hydrothermal treatment are not particularly limited, in order to efficiently proceed with the reaction, it is preferable to carry out the heating and pressurization so as to achieve a subcritical state. Although the reaction can also proceed in a supercritical state, this requires larger-scale equipment and increases operating costs. Therefore, it is appropriate to carry out the hydrothermal treatment in a subcritical state.

[0066] More specifically, the hydrothermal treatment is preferably carried out under the following conditions: Heating temperature: preferably 200 to 400°C, more preferably 250 to 374°C Pressure: preferably 5 to 30 MPa, more preferably 7 to 22.1 MPa Treatment time: preferably 10 to 120 minutes, more preferably 15 to 60 minutes

[0067] In this way, by performing oxygen reduction treatment such as aging treatment or hydrothermal treatment, it is possible to obtain a liquid fuel with a reduced oxygen content. In a typical case, the oxygen content of the liquid component before the oxygen reduction treatment is about 40 to 50 mass %, but by performing the oxygen reduction treatment, the oxygen content of the liquid fuel obtained is reduced to about 10 to 20 mass %.

[0068] When the fuel obtained in this way is to be used as a green chemical such as aviation fuel (SAF) or as a raw material for chemical products, it is preferable to further subject it to hydrorefining, as described above. However, even in this case, the oxygen content has been significantly reduced by the oxygen reduction treatment, so hydrorefining can be easily performed, and the amount of hydrogen and catalyst consumed can be significantly reduced.

[0069] The liquid fuel obtained in this manner is sometimes called biomass gas oil (BGO).

[0070] Any device can be used as the device for the oxygen reduction treatment (oxygen reduction treatment device) as long as it can maintain the liquid component under desired conditions. For example, the liquid component may be stored in a container (such as a chemical tank) equipped with a stirrer. In this case, the container is preferably equipped with a heat retention means.

[0071] When the oxygen reduction treatment is carried out by hydrothermal treatment, any device (hydrothermal treatment device) can be used as the oxygen reduction treatment device, as long as it can maintain the required temperature and pressure. For example, the treatment can be carried out in a batch system using a pressure-resistant container such as an autoclave. Alternatively, a continuous reaction device equipped with one or more reaction zones can be used.

[0072] The hydrothermal treatment device is preferably equipped with a pressure reduction system that cools and returns the pressure to normal after treatment is completed. For example, a surge tank or the like can be used as the pressure reduction system. Furthermore, it is preferable to recover heat during the cooling process and reuse the recovered heat for heating. After the pressure is reduced to normal pressure, it is preferable to transfer the obtained liquid fuel to a storage tank or the like for storage.

[0073] [Pulverization Step] Meanwhile, the solid component obtained in the pyrolysis step is pulverized to form a powder (pulverization step). The pulverization method is not particularly limited and can be any method, and may be wet pulverization or dry pulverization. The solid component can also be referred to as a "carbide." The powder obtained by pulverizing the solid component can also be referred to as a "pulverized carbide" or a "carbide powder."

[0074] The grinding device used for the grinding is not particularly limited, and any grinding device (grinding machine) can be used. Examples of the grinding device include a hammer mill, a ball mill, a tube mill, a rod mill, a jet mill, and a bead mill. From the viewpoint of increasing the circularity of the particles, it is preferable to use a bead mill.

[0075] When pulverization is performed using a bead mill, the circularity of the particles can be further improved by adjusting the operating conditions. Examples of the operating conditions include the amount of raw material input, the agitator rotation speed, and the material, size, and amount of the beads used. For example, using beads with a relatively small diameter reduces the impact force during pulverization, allowing frictional forces to prevail, thereby improving the circularity. Similarly, the circularity can also be improved by lowering the agitator rotation speed.

[0076] The size of the powder obtained in the above-mentioned pulverization step is not particularly limited, but excessively large particles will reduce the fluidity of the final slurry fuel. Therefore, from the viewpoint of improving the fluidity of the slurry fuel and making it easier to handle, it is preferable that the proportion of particles with a particle diameter of 100 μm or less in the powder be 95% or more, more preferably that the proportion of particles with a particle diameter of 50 μm or less be 95% or more on an area basis, and even more preferably that the proportion of particles with a particle diameter of 30 μm or less be 95% or more on an area basis. These proportions can be determined from the particle size distribution of the powder. A method for measuring the particle size distribution will be described later.

[0077] Furthermore, if the average particle diameter of the powder is excessively large, the fluidity of the slurry fuel will also decrease. Therefore, from the viewpoint of the fluidity of the slurry fuel, the average particle diameter is preferably 20 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, and most preferably 5 μm or less. On the other hand, if the average particle diameter is too small, the surface area of ​​the powder increases, thereby increasing the viscosity of the slurry fuel and resulting in a decrease in fluidity. Therefore, the average particle diameter is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. The average particle diameter can be determined from the particle size distribution of the powder.

[0078] The particle size distribution of the powder can be measured using a laser diffraction / scattering particle size distribution analyzer. A dynamic light scattering particle size analyzer can be used as the laser diffraction / scattering particle size distribution analyzer. The measurement can be performed after adding the powder to a 10% aqueous solution of naphthalenesulfonic acid-formalin condensate to a concentration of 10% by weight, and dispersing the dispersion for 15 minutes using an ultrasonic disperser. More specifically, the measurement can be performed using the method described in the Examples.

[0079] Average circularity: The circularity of the powder obtained by the above-mentioned pulverization step is not particularly limited. However, it is preferable that the average circularity of particles of the powder whose particle diameter in the volume-based particle size distribution is within ±10% of the average particle diameter (hereinafter, sometimes simply referred to as "average circularity") is 0.5 to 1.0. The reason for this is explained below.

[0080] When plant biomass is pyrolyzed, it is carbonized while retaining some of the original plant tissue structure, and therefore the individual particles that make up the powder after being pulverized in the above-mentioned pulverization process also retain the complex shapes derived from the plant tissue.

[0081] If the particles have an excessively complex shape, the interactions between the particles will be large, resulting in a decrease in dispersion fluidity when the powder is mixed with fuel oil or water in the subsequent mixing step. Furthermore, the viscosity of the resulting slurry fuel will increase. Therefore, from the perspective of improving dispersion fluidity and suppressing the increase in viscosity, it is desirable to thoroughly pulverize the solid components and increase the circularity of the particles constituting the powder.

[0082] Therefore, the average circularity is preferably 0.5 or more, more preferably 0.52 or more, even more preferably 0.55 or more, and most preferably 0.6 or more.

[0083] Here, the circularity φ of a particle is defined as the projected area A (m ２ ) and perimeter P (m) using the following formula: φ = 4πA / P. Therefore, the upper limit of the circularity is 1. ２

[0084] The circularity of each particle can be determined by photographing the powder to be measured while it is dispersed in a solvent and analyzing the resulting image. A dynamic particle image analyzer can be used to measure the circularity. More specifically, the circularity can be measured by the method described in the Examples.

[0085] The average circularity can be determined by averaging the circularities of particles of the powder whose particle diameters in the volume-based particle size distribution are within ±10% of the average particle diameter. As mentioned above, the particle size distribution of the powder can be measured using a laser diffraction / scattering particle size distribution analyzer.

[0086] In order to set the average circularity within the above range, it is sufficient to adjust the pulverization conditions in the pulverization step. By pulverizing the solid component more thoroughly, the viscosity increases as the surface area increases, but by pulverizing so that the average circularity falls within the above range, the increase in viscosity due to the increase in surface area can be suppressed.

[0087] The powder preferably has an ash content of 15% by mass or less, more preferably 10% by mass or less, and even more preferably 3% by mass or less. The ash content can be measured in accordance with JIS M8812:2004.

[0088] The powder preferably has a nitrogen content of 1.0% by mass or less, more preferably 0.7% by mass or less, and even more preferably 0.5% by mass or less. The nitrogen content can be measured in accordance with JIS M8813:2004.

[0089] The powder preferably has a sulfur content of 0.5% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less. The sulfur content can be measured, for example, according to JIS M8813:2004.

[0090] [Mixing step] Next, the powder obtained in the pulverization step is mixed with either fuel oil or water, or both, to obtain a slurry fuel (mixing step). The slurry fuel obtained by mixing the powder with fuel oil is sometimes called a biomass-oil mixed fuel (BOM). Similarly, the slurry fuel obtained by mixing the powder with water is sometimes called a biomass-water mixed fuel (BWM).

[0091] The mixing step can produce one or both of a BOM and a BWM, i.e., the mixing step includes one or both of a step of mixing the powder with fuel oil to produce a BOM and a step of mixing the powder with water to produce a BWM.

[0092] The mixing device used for the mixing is not particularly limited, and any agitator or disperser, such as a disperser, homogenizer, line mixer, or static mixer, can be used alone or in combination. The disperser may be, for example, an ultrasonic disperser. A pulverizer may also be used for the mixing. In this case, for example, the powder alone may first be pulverized in the pulverizer, and then fuel oil or water may be added and mixed. That is, the pulverization step and the mixing step may be carried out continuously using the pulverizer. In this case, the pulverizer serves as both a pulverizer and a mixer.

[0093] The mixing can be carried out in any atmosphere. For example, mixing may be carried out in air. However, from the viewpoint of preventing accidents such as explosions, it is preferable to carry out the mixing in an inert gas. For example, nitrogen can be used as the inert gas. Furthermore, it is preferable to carry out the mixing in an explosion-proof facility.

[0094] When the powder is mixed with fuel oil to prepare a slurry fuel (BOM), the content of the powder is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and most preferably 25% by mass or more, based on the total slurry fuel. On the other hand, the content of the powder is preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, and most preferably 45% by mass or less, based on the total slurry fuel. This allows the amount of fuel oil used to be more sufficiently reduced, and CO2 can be reduced more effectively. ２ can be reduced.

[0095] The viscosity of the slurry fuel is not particularly limited. However, lowering the viscosity improves the fluidity of the slurry fuel, thereby improving the ease of handling and transport of the slurry fuel. Therefore, the viscosity of the slurry fuel is preferably 1000 mPa·s or less, more preferably 800 mPa·s or less, even more preferably 600 mPa·s or less, and most preferably 500 mPa·s or less. On the other hand, the lower the viscosity, the easier it is to handle, so the lower limit of the viscosity is not particularly limited. However, the viscosity of the slurry fuel may typically be 10 mPa·s or more.

[0096] The viscosity can be measured using an E-type viscometer (cone-plate type viscometer) at 25° C. and 5 rpm. For example, a TV-100 rotor #1 manufactured by Toki Sangyo Co., Ltd. can be used as the viscometer.

[0097] The slurry fuel may have thixotropy or rheopexy properties, but preferably has thixotropy.

[0098] (Fuel Oil) The fuel oil is not particularly limited as long as it is an oil that can be used as a fuel, and any fuel oil can be used. In the case of fossil fuels, highly distilled products derived from crude oil are preferred. Liquid fuel oils such as light oil, heavy oil, kerosene, naphtha, gasoline, and jet fuel oil are more preferred, and light oil, heavy oil, and kerosene are even more preferred. Examples of the heavy oil include heavy oil A, heavy oil B, and heavy oil C.

[0099] The fuel oil may also contain one or both of bioalcohol and biodiesel. The bioalcohol is a biomass-derived alcohol such as ethanol, isopropanol, or butanol obtained by fermenting carbohydrates with bacteria or the like, and the biodiesel is a biodiesel fuel oil obtained by processing oils and fats obtained from vegetable oils, seaweed, or the like. Furthermore, the fuel oil may contain one or both of a liquid fuel produced by the production method of the present invention and a modified product thereof. From the perspective of reducing carbon dioxide emissions, it is preferable to minimize the amount of petroleum-based fuel oil and mix in more biofuel oil.

[0100] The viscosity of the fuel oil is not particularly limited, but is preferably 500 mPa s or less. More preferably, it is 300 mPa s or less, even more preferably 100 mPa s or less, and particularly preferably 50 mPa s or less. The viscosity of the fuel oil can be measured by the same method as the viscosity of the biomass-containing fuel. Meanwhile, the lower limit of the viscosity of the fuel oil is not limited, but may typically be 1 mPa s or more, or 5 mPa s or more.

[0101] On the other hand, when the powder is mixed with water to prepare a slurry fuel (BWM), the content of the powder is preferably 40 mass% or more, more preferably 43 mass% or more, even more preferably 45 mass% or more, and most preferably 50 mass% or more, based on the total amount of the slurry fuel. Also, the content of the powder is preferably 70 mass% or less, more preferably 65 mass% or less, even more preferably 65 mass% or less, and most preferably 60 mass% or less, based on the total amount of the slurry fuel.

[0102] (Water) The water is not particularly limited and any water can be used. Water generated during the pyrolysis of plant biomass and recovered can also be used as part or all of the water.

[0103] The water contained in the slurry fuel not only functions as a medium for dispersing the powder but also functions as a power energy source for driving the internal combustion engine, because when the slurry fuel is burned, the water evaporates and the volume expands.

[0104] The water content in the slurry fuel is not particularly limited and may be determined taking into consideration the amount of heat obtained by combustion of the powder (carbide). The water content is preferably 60 mass% or less, more preferably 57 mass% or less, even more preferably 55 mass% or less, and most preferably 50 mass% or less, based on the total amount of the slurry fuel. On the other hand, the water content is preferably 30 mass% or more, more preferably 35 mass% or more, and even more preferably 40 mass% or more, based on the total amount of the slurry fuel.

[0105] The theoretical value of the calorific value of the slurry fuel (BWM) obtained by mixing the powder with water is preferably 2000 to 8000 kcal / kg. It is more preferably 2500 to 7000 kcal / kg, and even more preferably 3000 to 6000 kcal / kg. The theoretical value of the calorific value can be calculated as follows: Calorific value = Calorific value of powder (measured value) × Powder content The calorific value of the slurry fuel can also be measured in accordance with JIS K2279:2003.

[0106] (Dispersant) The powder has excellent dispersibility in fuel oil, so it can be dispersed in fuel oil as it is. However, a dispersant can be added to further improve dispersibility. On the other hand, when mixing with water, it is desirable to use a dispersant.

[0107] When a dispersant is used, the content of the dispersant is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, more preferably 3 parts by mass or less, more preferably 1 part by mass or less, and more preferably 0.5 parts by mass or less, per 100 parts by mass of powder. On the other hand, since a dispersant is not essential, the lower limit of the content of the dispersant is not particularly limited and may be 0 parts by mass. However, when a dispersant is added, from the viewpoint of enhancing the effect of its addition, the content of the dispersant is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, per 100 parts by mass of powder.

[0108] The dispersant is not particularly limited and any dispersant can be used. For example, at least one selected from the group consisting of sulfonic acid dispersants, polycarboxylic acid dispersants, polyvinylpyrrolidone, polyacrylic acid, phosphoric acid dispersants, anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants can be used. Examples of dispersants that can be suitably used are listed below.

[0109] (i) Polyalkylarylsulfonate-based dispersants such as naphthalenesulfonic acid formaldehyde condensates; melamine formalin resin sulfonate-based dispersants such as melamine sulfonic acid formaldehyde condensates; aromatic aminosulfonate-based dispersants such as aminoarylsulfonic acid-phenol-formaldehyde condensates; lignin sulfonate-based dispersants such as lignin sulfonates and modified lignin sulfonates; polystyrene sulfonate-based dispersants; and various sulfonic acid-based dispersants having a sulfonic acid group in the molecule, such as nonylphenylol sulfonate.

[0110] (ii) As described in JP-B No. 59-18338 and JP-A No. 7-223852, copolymers obtained from polyalkylene glycol mono(meth)acrylate monomers, (meth)acrylic acid monomers, and monomers copolymerizable with these monomers; as described in JP-A Nos. 10-236858, 2001-220417, 2002-121055, and 2002-121056, copolymers obtained from unsaturated (poly)alkylene glycol ether monomers, maleic acid monomers, or (meth)acrylic acid monomers; and various polycarboxylic acid dispersants having a (poly)oxyalkylene group and a carboxyl group in the molecule.

[0111] (iii) Polyvinylpyrrolidone.

[0112] (iv) Polyacrylic acid.

[0113] (v) As described in JP-A-2006-52381, copolymers having a (poly)oxyalkylene group and a phosphate ester group in the molecule, such as copolymers obtained from (alkoxy)polyalkylene glycol mono(meth)acrylate, a phosphate monoester monomer, and a phosphate diester monomer; as described in JP-A-2008-517080, polycondensation products consisting of a monomer having a (poly)oxyalkylene group and an aromatic ring group and / or a heterocyclic aromatic group, a monomer having a phosphate (salt) group and / or a phosphate ester group and an aromatic ring group and / or a heterocyclic aromatic group, and an aldehyde compound; as described in JP-A-2015-508384, various phosphate dispersants such as dispersants having an aromatic triazine structural unit, a polyalkylene glycol structural unit, and a phosphate ester structural unit.

[0114] (vi) Anionic surfactants such as alkyl sulfates, higher alcohol sulfates, nonionic ether sulfates, olefin sulfates, polyoxyethylene alkyl (alkylphenol) sulfates, alkyl aryl sulfonates, dibasic acid ester sulfonates, alkyl benzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphates, and acyl sarcosinates.

[0115] (vii) Cationic surfactants such as alkylamine salts, quaternary amine salts, and alkylpyridinium sulfates.

[0116] (viii) nonionic surfactants such as polyoxyalkyl ethers, polyoxyethylene alkylphenol ethers, oxyethylene-oxypropylene block polymers, polyoxyethylene alkylamines, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, alkyltrimethylammonium chlorides, alkyldimethylbenzylammonium chlorides, polyoxyethylene fatty acid esters, aliphatic alcohol polyoxyethylene ethers, polyhydric alcohol fatty acid esters, and fatty acid ethanolamides;

[0117] (ix) Amphoteric surfactants such as alkylbetaines.

[0118] Among these, it is preferable to use a polycarboxylic acid-based dispersant as the dispersant. As the polycarboxylic acid-based dispersant, it is preferable to use a copolymer having a structural unit (a) derived from a polyalkylene glycol-based monomer (A) represented by the following formula (1) and a structural unit (b) derived from an unsaturated carboxylic acid-based monomer (B). Note that this polycarboxylic acid-based dispersant is particularly effective as a dispersant when mixed with water.

[0119] (In the formula, R １ , R ２ and R ３ are the same or different and represent a hydrogen atom or a methyl group. ４ represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. (R ５ O) are the same or different and represent an oxyalkylene group having 2 to 18 carbon atoms. n represents the average number of moles of oxyalkylene groups added and is a number from 1 to 300. x represents an integer from 0 to 4. y represents 0 or 1.

[0120] R in the above formula (1) ４ When is a hydrocarbon group, the hydrocarbon group preferably has 1 to 20 carbon atoms, more preferably 1 to 18 carbon atoms, even more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, and most preferably 1 to 3 carbon atoms.

[0121] Examples of the hydrocarbon group include linear or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, 3-pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, isooctyl, 2,3,5-trimethylhexyl, 4-ethyl-5-methyloctyl, 2-ethylhexyl, tetradecyl, octadecyl, and icosyl groups; phenyl groups, methylphenyl groups, ethylphenyl groups; naphthyl groups; benzyl groups, 1-phenylethyl groups, 2-phenylethyl groups, 3-phenylpropyl groups, 4-phenylbutyl groups, styryl groups (Ph-CH=C- groups), and cinnamyl groups (Ph-CH=CHCH２ - group), 1-benzocyclobutenyl group, 1,2,3,4-tetrahydronaphthyl group and other aromatic hydrocarbon groups are preferred.

[0122] In the above formula (1), n ​​is preferably 1 to 100, more preferably 1 to 80, and even more preferably 1 to 50.

[0123] In the above formula (1), R ５ O may be the same or different and represent an oxyalkylene group having 2 to 18 carbon atoms. ５ This means that all of the oxyalkylene groups represented by O may be the same or different.

[0124] The oxyalkylene group preferably has 2 to 18 carbon atoms, more preferably 2 to 12 carbon atoms, even more preferably 2 to 8 carbon atoms, and particularly preferably 2 to 4 carbon atoms.

[0125] In the above formula (1), R ５ The oxyalkylene group represented by O is an alkylene oxide adduct, and examples of such alkylene oxides include alkylene oxides having 2 to 8 carbon atoms such as ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, 1-butene oxide, 2-butene oxide, and styrene oxide. More preferred are alkylene oxides having 2 to 4 carbon atoms such as ethylene oxide, propylene oxide, and butylene oxide.

[0126] The unsaturated monocarboxylic acid monomer (B) is not particularly limited as long as it is a monomer having an unsaturated group and a group capable of forming a carbanion in the molecule, and examples thereof include (meth)acrylic acid, crotonic acid, isocrotonic acid, tiglic acid, 3-methylcrotonic acid, 2-methyl-2-pentenoic acid, α-hydroxyacrylic acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, fumaric acid, and salts thereof. Preferred are (meth)acrylic acid, maleic acid, and salts thereof.

[0127] The content of the structural unit (a) in the copolymer is not particularly limited, but is preferably 1 to 95% by mass, more preferably 5 to 70% by mass, even more preferably 7 to 60% by mass, and particularly preferably 10 to 50% by mass, relative to 100% by mass of all structural units.

[0128] The content of the structural unit (b) in the copolymer is not particularly limited, but is preferably 5 to 99% by mass, more preferably 30 to 95% by mass, even more preferably 40 to 93% by mass, and particularly preferably 50 to 90% by mass, relative to 100% by mass of all structural units.

[0129] The weight average molecular weight of the dispersant is not particularly limited, but is typically preferably 100 to 1,000,000.

[0130] When the powder is mixed with fuel oil to prepare a slurry fuel (BOM), the weight average molecular weight is preferably 100 to 100,000, more preferably 200 to 500,000, and even more preferably 300 to 100,000.

[0131] On the other hand, when the powder is mixed with water to prepare a slurry fuel (BWM), the weight average molecular weight is preferably 1,000 to 1,000,000, more preferably 2,000 to 500,000, and even more preferably 3,000 to 100,000. When the weight average molecular weight is 1,000 or more, foaming during dispersion can be more sufficiently suppressed.

[0132] When the dispersant is a polycarboxylic acid-based dispersant, the weight average molecular weight is preferably 3,000 to 500,000, more preferably 4,000 to 300,000, even more preferably 5,000 to 100,000, still more preferably 10,000 to 80,000, and even more preferably 20,000 to 60,000.

[0133] The weight average molecular weight of the dispersant can be measured by a standard polystyrene conversion method using gel permeation chromatography (GPC).

[0134] The slurry fuel may contain components other than the powder and fuel oil or water. The other components are not particularly limited, but may include, for example, at least one selected from the group consisting of stabilizers, separation reducing agents, thickeners, viscosity reducing agents, other biofuels, ignition agents, cetane number improvers, lubricants, organic solvents, and water retention agents. In particular, in the case of BOM, stabilizers, separation reducing agents, thickeners, viscosity reducing agents, biofuels, ignition agents, cetane number improvers, lubricants, etc. are preferably added. In addition, in the case of BWM, stabilizers, thickeners, viscosity reducing agents, ignition agents, organic solvents, water retention agents, lubricants, etc. are preferably added.

[0135] The content of the other components is not particularly limited, but is preferably 20 mass% or less, more preferably 10 mass% or less, and even more preferably 5 mass% or less, based on the total amount of the slurry fuel. The lower limit of the content of the other components may be 0 mass%.

[0136] The stabilizer is not particularly limited, but for example, in the case of BOM, examples include polyalkylene oxide adducts of alcohols, among which polyalkylene oxide adducts of glycerin are preferred. Furthermore, in the case of BWM, examples include ammonia, sodium hydroxide, amines, and the like, among which ammonia is preferred.

[0137] The thickener is not particularly limited, but examples thereof include polysaccharides, polyacrylamides, polyalkylene oxides, polyacrylic acids and salts thereof, and polyvinyl alcohols.

[0138] The viscosity reducing agent is not particularly limited, but examples thereof include glycol monoethers, glycol diethers, phenyl glycol ethers, and benzyl glycols.

[0139] The ignition agent is not particularly limited, but examples thereof include heavy oil, light oil, bioalcohol, etc. Among these, biobutanol, biopropanol, and bioethanol are preferred.

[0140] The organic solvent is not particularly limited, but examples thereof include alcohols having 1 to 8 carbon atoms, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and phenoxyethanol; glycols, such as ethylene glycol, propylene glycol, butylene glycol, and hexylene glycol; acetone; and ethyl acetate.

[0141] In this way, the powder can be mixed with fuel oil or water to produce a slurry fuel. The obtained slurry fuel can be suitably used as a fuel for diesel engines and gas turbine engines. In particular, a slurry fuel (BOM) obtained by mixing the powder with fuel oil can be used as a fuel in existing diesel engines as is. Furthermore, a slurry fuel (BWM) obtained by mixing the powder with water can be used as a fuel in gas turbine engines. Furthermore, since BWM does not contain fossil fuels, it can be said to be a carbon-neutral fuel.

[0142] Fig. 2 is a flow diagram showing a fuel production method according to one embodiment of the present invention. As shown in Fig. 2, the fuel production method of this embodiment further comprises the following steps (6) and (7) in addition to the above-mentioned steps (1) to (5). Note that, although an example in which both steps (6) and (7) are performed will be described here, it is also possible to perform only one of steps (6) or (7). (6) First hydrogen production step (7) Second hydrogen production step

[0143] [First hydrogen production step] In the liquefaction step, the gaseous components obtained by pyrolysis of plant biomass are liquefied, but some components (off-gas) remain in the gaseous state without being liquefied. The components of this off-gas vary depending on the type of plant biomass used and the pyrolysis conditions, but typically contain about 70% CO ２ The off-gas contains about 15-20% CO, about 5-8% hydrogen, about 10% hydrocarbons (methane, ethane, etc.), and the remainder is nitrogen, water vapor, etc. Therefore, by producing hydrogen from this off-gas, plant biomass can be used more effectively.

[0144] [Second Hydrogen Production Step] In the hydrothermal treatment step, the liquid component is hydrothermally treated to obtain a liquid fuel, and off-gas is also produced as a by-product during this process. This off-gas contains CO, CO ２ , H ２ O, H ２ Therefore, by producing hydrogen from this off-gas, plant biomass can be used more effectively.

[0145] The method for producing hydrogen in the first hydrogen production process and the second hydrogen production process is not particularly limited, and any method can be applied alone or in combination. The method for producing hydrogen in the first hydrogen production process and the second hydrogen production process is not particularly limited, and any method can be used. Furthermore, any device (first hydrogen production device) can be used in the first hydrogen production process. Similarly, any device (second hydrogen production device) can be used in the second hydrogen production process.

[0146] The first hydrogen production step and the second hydrogen production step may be performed separately or together. That is, hydrogen production from the first off-gas and hydrogen production from the second off-gas may be performed separately, or hydrogen may be produced using a mixed gas obtained by mixing the first off-gas and the second off-gas. In this case, one hydrogen production device can be used as the first hydrogen production device and the second hydrogen production device.

[0147] One suitable method for producing hydrogen is to separate hydrogen gas contained in the off-gas. Various methods are known for separating hydrogen gas from a mixed gas, and any of these methods can be used in this embodiment. For example, it is also preferable to perform separation using a molecular sieve.

[0148] Another suitable method for producing hydrogen is to produce hydrogen from CO contained in the off-gas by the water-gas shift reaction.

[0149] Another suitable method for producing hydrogen is to produce hydrogen from hydrocarbons such as methane contained in the off-gas by steam reforming, in which any catalyst such as a Ni catalyst can be used.

[0150] The green hydrogen obtained in this way can be used for a variety of purposes, such as fuel for fuel cells or rocket fuel.

[0151] As described above, according to the present invention, highly useful fuel can be produced extremely efficiently using plant biomass as a raw material.

[0152] Next, the present invention will be described in more detail based on specific examples. Note that the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0153] Example 1 First, tests were conducted to obtain a solid component (charcoal) and a liquid component by pyrolyzing plant biomass at 400°C (Tests No. 1 to 3). Specifically, each of the three types of plant biomass shown in Table 1 was pyrolyzed at atmospheric pressure and a temperature of 400°C. A rotary kiln-type carbonization furnace with a rated processing rate of 20 kg / h and equipped with baffles inside was used for the pyrolysis. The processing time (the time from loading into the carbonization furnace to discharging) was approximately 60 minutes. The weight of the plant biomass (raw material supply amount) subjected to pyrolysis and the moisture content of the plant biomass used are also shown in Table 1. The cedar and acacia were in pellet form, and the bagasse was in fibrous form.

[0154] After pyrolysis was carried out under the above conditions, the remaining solid components were recovered as they were. The gaseous components generated by pyrolysis were liquefied by cooling to ambient temperature (approximately 30°C) using a scrubber, and were recovered as liquid components. The recovery amounts and recovery rates of the recovered solid and liquid components were as shown in Table 1. The recovery rate was calculated using the following formula: Recovery rate = recovery amount (kg) / raw material supply amount (kg) x 100

[0155] Furthermore, the ash content, volatile matter, fixed carbon, and higher heating value of the solid components obtained in each of the above Tests No. 1 to 3 were analyzed. The analytical results are shown in Table 2. These analytical results are measured on an anhydrous basis. For reference, the fuel ratio (= fixed carbon / volatile matter) is also shown in Table 2.

[0156] The results shown in Table 1 demonstrate that pyrolysis under the conditions of the present invention allows for the appropriate recovery of solid and liquid components from any plant biomass. Furthermore, as shown in Table 2, all of the solid components obtained had sufficient calorific value. Furthermore, all of the solid components had an ash content of 15% by mass or less, a nitrogen content of 1.0% by mass or less, and a sulfur content of 0.05% by mass or less.

[0157]

[0158]

[0159] (Example 2) Next, tests were conducted to obtain a solid component (carbonized material) and a liquid component by pyrolysis at different pyrolysis temperatures (Test Nos. 4 to 6). Cedar was used as the raw plant biomass, and the other conditions were the same as in Example 1 above. The analysis results of the obtained solid component are shown in Table 3.

[0160] As can be seen from the results shown in Table 3, solid components with sufficient calorific value can be obtained at any pyrolysis temperature. Note that in Example 1 (Table 2) No. 1 and Example 2 (Table 3) No. 5, both cedar trees were pyrolyzed at 400°C, but the analysis results of the solid components differ. This is because even the same type of plant biomass has different properties depending on the place of origin, harvest time, etc. Furthermore, although not detailed here, the recovery rates of the solid and liquid components were similar to those in Example 1.

[0161]

[0162] (Example 3) Next, a test was conducted to confirm the effect of the oxygen reduction treatment. Specifically, the liquid component obtained in No. 1 of Example 1 above was subjected to oxygen reduction treatment under two conditions to produce liquid fuel. Under the first condition, the liquid component was placed in a pail and subjected to aging treatment in which it was stored at room temperature and atmospheric pressure for one and a half years (No. 1-2). Under the second condition, the liquid component was subjected to hydrothermal treatment in a subcritical state (No. 1-3). The hydrothermal treatment in the subcritical state was performed for 30 minutes at a temperature of approximately 300°C and a pressure of approximately 27 MPa.

[0163] After the oxygen reduction treatment, the obtained fuel was subjected to elemental analysis to measure the amounts of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N). The amount of nitrogen was measured using the analytical method specified in JIS K 2609, and the amounts of other elements were measured using an elemental analyzer. The measurement results are shown in Table 4. For comparison, the elemental analysis results of a liquid component that was not subjected to oxygen reduction treatment are also shown in Table 4 (No. 1-1).

[0164] The results shown in Table 4 show that the amount of oxygen can be reduced to about 20% by performing the oxygen reduction treatment.

[0165] Furthermore, when the obtained liquid fuel was dissolved in various solvents, it was confirmed that the compatibility was improved. For example, the liquid component before the oxygen reduction treatment was slightly soluble in diesel oil and kerosene, but the liquid fuel after the oxygen reduction treatment was more soluble in diesel oil and kerosene than the liquid component before the oxygen reduction treatment.

[0166]

[0167] (Example 4) Next, slurry fuels (BOM) were produced using the solid component (carbide) obtained in No. 1 of Example 1 (Nos. 10 to 12). Specifically, the solid component was first coarsely pulverized using a commercially available hammer mill, and then powder with an average particle size of 5 μm was obtained using a commercially available fine pulverizer. Next, the powder was mixed with fuel oil in a nitrogen atmosphere for at least one hour. After that, the mixture was filtered using a 200-mesh wire screen to obtain a slurry fuel. Nos. 10 to 12 each had the following composition. No. 10: 30 mass% carbide powder, balance A heavy oil. No. 11: 30 mass% carbide powder, 3 mass parts of dispersant (relative to 100 mass parts of carbide powder), balance A heavy oil. No. 12: 15 mass% carbide powder, balance A heavy oil.

[0168] The properties of the obtained slurry fuel were measured. The test methods used and the results are shown in Table 5. For comparison, data on ordinary heavy oil A without any carbide mixed in is also shown in Table 5. As can be seen from these results, the slurry fuel (BOM) obtained by the method of the present invention has properties that make it suitable for use as a fuel.

[0169]

[0170] Example 5 A slurry fuel (BWM) was prepared by dispersing the same carbide powder as used in Example 4 in water. The content of the carbide powder in the slurry fuel was 50 mass %.

[0171] A polycarboxylic acid-based dispersant was used as the dispersant. The polycarboxylic acid-based dispersant was a copolymer of methacrylic acid (MAA) and methoxypolyethylene glycol methacrylate (average number of moles of ethylene oxide added: 25) (PGM25E), with a mass ratio of MAA to PGM25E of MAA:PGM25E = 80:20 and a weight-average molecular weight of 23,000. The content of the dispersant was 3 parts by mass per 100 parts by mass of the powder.

[0172] The higher heating value of the obtained slurry fuel was measured and found to be 15,530 kJ / kg. As can be seen from this result, the slurry fuel (BWM) obtained by the method of the present invention has properties that make it suitable for use as a fuel.

[0173] Example 6 Next, the following test was carried out to confirm the effect of the circularity of the powder (carbide powder) on the viscosity of the slurry fuel.

[0174] Cedar was pyrolyzed under the same conditions as in Example 1 (pyrolysis temperature: 400°C) to recover solid components. The carbonized material was coarsely pulverized using a commercially available hammer mill (RT-34, manufactured by LaboNext Co., Ltd.), and then finely pulverized using a Pulvis PV-150 (manufactured by Hosokawa Micron Corporation) under the following operating conditions, yielding carbonized pulverized products with the average particle sizes listed in Table 6 (Nos. 30 to 36). However, for No. 36, after the coarse pulverization, the powder was classified using a sieve with 20 μm openings to obtain a powder with an average particle size of 20.2 μm.

[0175] The average circularity of the carbonized pulverized material of each particle size was as shown in Table 6. The average particle size and average circularity were measured by the method described above. <Operating conditions of the fine pulverizer> Media: 4.5 kg of 3 mm stainless steel beads Raw material feeding rate: 5 to 20 g / min Pulverizer rotation speed: 300 to 600 rpm Classifier rotation speed: 4000 to 23000 rpm Bottom gas flow rate: 0.1 to 0.4 Nm ３ / min

[0176] The resulting powder was slowly added to diesel fuel and stirred for 1 hour to produce a slurry fuel (BOM). The amount of the powder in the slurry fuel was 30 mass%. The viscosity of the resulting slurry fuel is also shown in Table 6. The viscosity was measured by the method described above.

[0177]

[0178] Example 7 Next, the following test was carried out to confirm the influence of the circularity of the powder (carbide powder) on the viscosity of the slurry fuel.

[0179] The same powder as used in Example 6 was dispersed in water to prepare a slurry fuel (BWM). A polycarboxylic acid-based dispersant was used. The polycarboxylic acid-based dispersant was a copolymer of methacrylic acid (MAA) and methoxypolyethylene glycol methacrylate (average number of moles of ethylene oxide added: 25) (PGM25E). The mass ratio of MAA to PGM25E was 80:20, and the weight-average molecular weight was 23,000. The content of the dispersant was 3 parts by mass per 100 parts by mass of the powder.

[0180] The content of the powder in the slurry fuel was as shown in Table 7. The viscosity of the obtained slurry fuel is also shown in Table 7. The viscosity was measured by the method described above.

[0181]

Claims

1. A fuel production method comprising: a pyrolysis process for pyrolyzing plant biomass at 350-430°C to obtain gaseous and solid components; a liquefaction process for cooling the gaseous component to obtain a liquid component; an oxygen reduction process for reducing the oxygen in the liquid component to obtain a liquid fuel; a crushing process for crushing the solid component to obtain a powder; and a mixing process for mixing the powder with either fuel oil or water, or both, to obtain a slurry fuel.

2. The fuel production method according to claim 1, further comprising a first hydrogen production step of producing hydrogen from a first off-gas that was not liquefied in the liquefaction step.

3. The fuel production method according to claim 1 or 2, further comprising a second hydrogen production step of producing hydrogen from a second off-gas by-produced in the oxygen reducing treatment step.

4. A fuel production method according to any one of claims 1 to 3, wherein the powder has an average circularity of 0.5 to 1 for particles whose particle size in a volume-based particle size distribution falls within ±10% of the average particle size.

5. A fuel production system comprising: a pyrolysis device for pyrolyzing plant biomass at 350-430°C to obtain gaseous and solid components; a liquefaction device for cooling the gaseous component to obtain a liquid component; an oxygen reduction treatment device for reducing the oxygen in the liquid component to obtain a liquid fuel; a crushing device for crushing the solid component to obtain a powder; and a mixing device for mixing the powder with either fuel oil or water, or both, to obtain a slurry fuel.

6. The fuel production system according to claim 5, further comprising a first hydrogen production unit that produces hydrogen from a first off-gas that was not liquefied in the liquefaction unit.

7. The fuel production system according to claim 5 or 6, further comprising a second hydrogen production system which produces hydrogen from a second off-gas by-produced in the oxygen reducing treatment system.

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