WO2025121379A1 - Fuel production method and fuel production device - Google Patents

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

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

In order to curb global warming, efforts to reduce greenhouse gas emissions are being made on a global scale. In particular, it is urgent to reduce energy-related _CO2 emissions, which account for the majority of greenhouse gas emissions.

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 this with "sustainable aviation fuel (SAF)" derived from biomass and other sources. In addition, diesel and heavy oil are widely used as fuels in various engines, including industrial and marine engines, but it is hoped that these fuels will also be replaced with fuels derived from biomass.

In this context, there has been active research into technologies to produce alternative fuels to fossil fuels from plant biomass. Because plants absorb _CO2 from the atmosphere during their growth process, the use of fuels derived from plant biomass does not increase the amount of _CO2 in the atmosphere (carbon neutral).

One of the most common ways to utilize plant biomass is to use the carbonized material obtained by steaming wood and other materials as solid fuel. However, since the solid carbonized material cannot be used as aviation fuel or fuel for diesel engines, its use is limited.

As described in Patent Document 1, research is being conducted into producing liquid fuel from gaseous components obtained by heating plant biomass.

JP 2023-156900 A

In this way, the products produced when biomass is pyrolyzed vary depending on the pyrolysis temperature. Thermal decomposition at high temperatures increases the proportion of gaseous components, while at low temperatures the solid content increases.

(1) For example, when the goal is to produce solid fuel from biomass, pyrolysis must be carried out at low temperatures (typically around 200-300°C) to increase the yield of solids. Pyrolysis carried out at such low temperatures is called "torrefaction."

(2) On the other hand, if 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 high temperatures (typically around 500-600°C). Pyrolysis carried out at such high temperatures is called "fast pyrolysis."

(3) There is also a known method of synthesizing 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 break down the biomass into hydrogen and carbon monoxide.

As mentioned above in (1) to (3), in the past, in order to increase the yield of the desired product (solid or gaseous components), 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 performed in the intermediate temperature range, gaseous components and solids are obtained in similar proportions, but until now there has been no technology to effectively use both as fuel.

The inventors conducted research to solve the above problems and came to the following findings.

(1) By liquefying the gaseous components obtained by pyrolysis of plant biomass and then subjecting it to an oxygen reduction process, 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 obtained in this way can be further hydrorefined as necessary and then suitably used for applications such as aviation fuel and raw material for chemical products.

(2) On the other hand, the solid components 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 way 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 fuels and can therefore be said to be a carbon-neutral fuel.

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

(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 differentiation of plant biomass within a specific range of 350 to 430°C.

The present invention has been made to solve the above problems, and its main features are as follows:

1. A pyrolysis step in which plant biomass is pyrolyzed at 350 to 430°C to obtain gaseous and solid components;
a liquefaction step of cooling the gas component to obtain a liquid component;
an oxygen reducing treatment step for reducing oxygen in the liquid component to obtain a liquid fuel;
a grinding step of grinding the solid component to obtain a powder;
A mixing step of mixing the powder with either or both of fuel oil and water to obtain a slurry fuel.

2. The fuel production method described in 1 above, further comprising a first hydrogen production process for producing hydrogen from a first off-gas that was not liquefied in the liquefaction process.

3. The fuel production method described in 1 or 2 above, further comprising a second hydrogen production process for producing hydrogen from the second off-gas by-produced in the oxygen reduction process.

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 size in the volume-based particle size distribution is within ±10% of the average particle size.

5. A pyrolysis device for pyrolyzing plant biomass at 350 to 430°C to obtain gaseous and solid components;
a liquefaction device for cooling the gas component to obtain a liquid component;
an oxygen reducing treatment device for reducing oxygen in the liquid component to obtain a liquid fuel;
a grinding device for grinding the solid component to obtain a powder;
and a mixer for mixing the powder with fuel oil and/or water to obtain a slurry fuel.

6. The fuel production apparatus described in 5 above, further comprising a first hydrogen production device that produces hydrogen from a first off-gas that was not liquefied by the liquefaction device.

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

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

FIG. 1 is a flow diagram showing a fuel production method according to an embodiment of the present invention. FIG. 4 is a flow diagram showing a fuel production method according to another embodiment of the present invention.

Next, we will explain in detail how to implement the present invention.

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 the present embodiment includes the following steps (1) to (5).
(1) Pyrolysis process (2) Liquefaction process (3) Oxygen reduction process (4) Pulverization process (5) Mixing process

Moreover, the fuel production apparatus in one embodiment of the present invention includes the following (A) to (E) corresponding to each of the above steps (1) to (5).
(A) Thermal decomposition device (B) Liquefaction device (C) Oxygen reduction device (D) Crushing device (E) Mixing device

The following describes each of the above steps and devices.

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

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.

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 millet, walnut, sawara, kaya, yew, oak, katsura, and fir. Of these, it is preferable to use at least one of cedar and acacia.

Herbaceous biomass includes, but is not limited to, rice (straw, rice husk), wheat (straw, rice husk), buckwheat (straw, rice husk), sugarcane, erianthus, corn, rapeseed, soybean, palm, reed, bamboo, bamboo, sugar beet, etc. Fruits (husks, residues after squeezing juice, 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.

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, or chips, bark, pomace, lumber residue, or pruning residue.

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 gas 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 it too much, the time and energy required for pre-drying will increase, and productivity will decrease. Therefore, the moisture content may be 5% by weight or more.

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.

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

Plant biomass is mainly composed of cellulose and hemicellulose, which are polysaccharides, and lignin, which is a polymeric compound containing aromatic rings. In the present invention, pyrolysis is performed at a relatively low temperature of 350 to 430°C, which allows the cellulose and hemicellulose to be selectively pyrolyzed and volatilized. On the other hand, lignin hardly pyrolyzes in this temperature range, so it remains as a solid component. Therefore, the liquid component (pyrolysis oil) obtained by liquefying the volatilized gas components is relatively light (it has 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 as a raw material for chemical products.

It is common to produce carbonized materials such as charcoal by pyrolyzing plant biomass, but pyrolysis is usually carried out at a higher temperature, so the resulting carbonized material contains almost no volatile components (oil). In contrast, in the present invention, pyrolysis is carried out at a low temperature of 350 to 400°C, so a relatively large amount of oil remains in the resulting solid component (carbonized material). Therefore, as described below, slurry fuel, which is made by mixing the solid components with fuel oil, has the same level of ignition ability as light oil or heavy oil. The slurry fuel also has the same lubricity and wear resistance as heavy oil A.

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

The atmosphere in which the pyrolysis is carried out is not particularly limited, but it is preferable that the oxygen concentration in the atmosphere is less than 5%, and more preferably less than 3%. The oxygen concentration can be achieved, for example, by carrying out the pyrolysis in a furnace in which the pyrolysis is carried out while the inside of the furnace is sealed off from the outside air. This is because the oxygen in the furnace is consumed as the pyrolysis progresses, and the inside of the furnace becomes substantially oxygen-free. It is also possible to create an inert gas atmosphere in which the oxygen concentration is reduced 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 it may be 0%.

The processing 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 processing time is not limited either, but is preferably 120 minutes or less, more preferably 90 minutes or less, and even more preferably 80 minutes or less.

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

When using a batch furnace, the heating rate is not particularly limited, and heating can be performed at any rate. For example, the heating rate is 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 heating rate is preferably 50°C/min or less, more preferably 20°C/min or less, and even more preferably 10°C/min or less.

When a rotary kiln is used, 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 per minute.

The kiln may typically be of an externally heated type. Baffles or the like may be installed on the inner surface of the kiln to promote mixing and stirring.

[Liquefaction process]
Next, the gas component generated in the above pyrolysis step is cooled to obtain a liquid component (liquefaction step).

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 contacting the liquid components in the scrubber. It is preferable that the liquid components are cooled by heat exchange with cooling water and circulated.

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 less, more preferably 95°C or less, preferably 40°C or less, more preferably 35°C or less, and even more preferably 30°C or less. For example, cooling to ambient temperature (room temperature) may be performed. On the other hand, since excessive cooling is not necessary, the cooling temperature may be 0°C or more, 5°C or more, or 10°C or more. In addition, when performing the aging treatment at a temperature higher than room temperature as described later, the cooling temperature is preferably 70°C or more, and more preferably 80°C or more. By performing liquefaction at a relatively high temperature in this way, the energy required for heating for the aging treatment can be reduced.

The composition of the liquid component obtained in the liquefaction process 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 obtained, 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% to 60% by weight.

In addition, since the liquid component is derived from plant biomass, the sulfur content tends to be extremely low, and usually contains substantially no sulfur. The sulfur content in the liquid component is, for example, 0.5% by weight or less, and preferably 0.1% by weight or less. The lower limit of the sulfur content is not particularly limited, but may be 0%.

The gaseous components generated in the pyrolysis process contain mist, and this mist may contain fine carbides and the like. If the subsequent processing is carried out while the carbides and the like are still present, the quality of the liquid fuel finally obtained will decrease. 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 process prior to the liquefaction process (mist removal process). A cyclone-type mist separator or the like can be used to remove the mist.

[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, since it is strongly acidic and hydrophilic, it is not compatible with general fuels and cannot be used by mixing it.

The oxygen content is reduced by subjecting the liquid component to oxygen reduction treatment. Reducing the oxygen content not only increases the calorific value, but also improves compatibility with other fuels. The liquid fuel obtained by subjecting the liquid component to oxygen reduction treatment can be used as fuel for diesel engines, etc. Furthermore, by further subjecting it 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.

The method of the oxygen reduction treatment is not particularly limited, and any method that can reduce the oxygen content can be used. A suitable method of oxygen reduction treatment is described below.

Aging Treatment The present inventors have found that the oxygen content can be reduced by simply 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". It is believed that the oxygen content is reduced by the aging treatment because dehydration condensation of the pyrolysis product contained in the liquid component progresses. This dehydration condensation reaction proceeds slowly even at normal temperature and normal pressure, so heating is not essential in the aging treatment. In other words, the oxygen reduction treatment can be performed by simply holding the liquid component at normal temperature (ambient temperature) without heating.

However, the speed of chemical reactions depends on temperature, so if the temperature is low, the deoxidation process will take a long time. Therefore, the temperature at which the aging process is carried out (aging temperature) is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher.

From the viewpoint of further shortening the processing time, the aging treatment can be performed at a higher temperature. In this case, the aging temperature is not particularly limited, and it is sufficient that the temperature is higher than room temperature (ambient temperature). However, from the viewpoint of effectively shortening the processing 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.

When aging is performed at a temperature higher than room temperature, the liquid component can be heated as necessary. Also, 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 process can be performed by placing the liquid component in a tank or the like and keeping it warm.

The time for which the aging treatment is carried out (treatment time) is not particularly limited and may be determined so as to obtain the desired effect. For example, when the aging treatment is carried out 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 excessively 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.

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

- Hydrothermal treatment In another embodiment, the liquid component can be heated and pressurized to perform the oxygen reduction treatment. The treatment of heating and pressurization in this way is generally called hydrothermal treatment. The liquid component obtained by pyrolyzing the plant biomass under the above conditions usually contains moisture. Therefore, in this hydrothermal treatment, heating and pressurization are performed in a state where moisture is present. However, the hydrothermal treatment may be performed after further adding moisture to the liquid component.

The specific conditions for the hydrothermal treatment are not particularly limited, but in order to allow the reaction to proceed efficiently, it is preferable to carry out the heating and pressurization so as to create a subcritical state. The reaction can also proceed in a supercritical state, but this requires larger equipment and increases operating costs. For this reason, it is appropriate to carry out the hydrothermal treatment in a subcritical state.

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

In this way, by carrying out oxygen reduction treatments such as aging and hydrothermal treatment, liquid fuel with reduced oxygen content can be obtained. In a typical case, the oxygen content of the liquid component before the oxygen reduction treatment is about 40-50 mass%, but by carrying out the oxygen reduction treatment, the oxygen content of the liquid fuel obtained is reduced to about 10-20 mass%.

If 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 carry out hydrorefining treatment, as described above. However, even in this case, the oxygen content is significantly reduced by the above-mentioned oxygen reduction treatment, so hydrorefining can be carried out easily, and the amount of hydrogen and catalyst consumed can be significantly reduced.

The liquid fuel obtained in this way is sometimes called biomass gas oil (BGO).

Any device can be used as the device used for the above-mentioned oxygen reduction treatment (oxygen reduction treatment device) as long as it can hold the liquid component under the desired conditions. For example, the liquid component can be stored in a container (such as a chemical tank) equipped with an agitator. In this case, it is preferable that the container is equipped with a heat retention means.

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 without any particular limitations as long as it can maintain the required temperature and pressure. For example, the treatment can be carried out in a batch manner using a pressure-resistant container such as an autoclave. A continuous reaction device equipped with one or more reaction zones can also be used.

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

[Crushing process]
On the other hand, the solid component obtained in the pyrolysis step is pulverized to obtain a powder (pulverization step). The method for pulverization is not particularly limited and may be any method, and may be wet pulverization or dry pulverization. The solid component may also be called "carbide". The powder obtained by pulverizing the solid component may also be called "pulverized carbide" or "carbide powder".

The grinding device used for the grinding is not particularly limited, and any grinding device (crusher) 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.

When grinding using a bead mill, the circularity of the particles can be 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, if beads with a relatively small diameter are used, the impact force during grinding is reduced and frictional forces become dominant, resulting in improved circularity. Similarly, circularity can also be improved by lowering the agitator rotation speed.

The size of the powder obtained in the above grinding process is not particularly limited, but if the particles are too large, the fluidity of the final slurry fuel will decrease. Therefore, from the viewpoint of increasing the fluidity of the slurry fuel and making it easier to handle, it is preferable that the proportion of particles in the powder having a particle diameter of 100 μm or less is 95% or more, more preferably that the proportion of particles having a particle diameter of 50 μm or less is 95% or more on an area basis, and even more preferably that the proportion of particles having a particle diameter of 30 μm or less is 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.

Also, if the average particle diameter of the powder is too 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 will increase, 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.

The particle size distribution of the powder can be measured using a laser diffraction/scattering type particle size distribution measuring device. A dynamic light scattering particle size measuring device can be used as the laser diffraction/scattering type particle size distribution measuring device. The measurement can be performed after adding the powder to a 10% aqueous solution of naphthalenesulfonic acid-formalin condensate so that the powder becomes 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.

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

When plant biomass is pyrolyzed, it is carbonized while retaining some of the original plant tissue structure. As a result, the individual particles that make up the powder after being pulverized in the above-mentioned crushing process retain the complex shapes derived from the plant tissue.

If the particles have an overly complex shape, the interactions between the particles will be greater, resulting in a decrease in dispersion fluidity when the powder is mixed with fuel oil or water in the next mixing step. In addition, 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 that make up the powder.

Therefore, it is preferable that the average circularity is 0.5 or more, more preferably 0.52 or more, even more preferably 0.55 or more, and most preferably 0.6 or more.

Here, the circularity φ of a particle is a dimensionless number calculated from the projected area A (m ² ) and perimeter P (m) of the particle by the following formula: Therefore, the upper limit of the circularity is 1.
φ=4πA/ ^P2

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 using the method described in the Examples.

The average circularity can be determined by averaging the circularity of particles of the powder whose particle size in the volume-based particle size distribution is within ±10% of the average particle size. As mentioned above, the particle size distribution of the powder can be measured using a laser diffraction/scattering particle size distribution measuring device.

In order to bring the average circularity into the above range, the grinding conditions in the grinding process can be adjusted. By grinding the solid components more thoroughly, the viscosity increases with an increase in surface area, but by grinding so that the average circularity falls within the above range, the increase in viscosity that occurs with an increase in surface area can be suppressed.

The powder preferably has an ash content of 15% by mass or less. More preferably, it is 10% by mass or less, and even more preferably, it is 3% by mass or less. The ash content can be measured according to JIS M8812:2004.

The nitrogen content of the powder is preferably 1.0% by mass or less. More preferably, it is 0.7% by mass or less, and even more preferably, it is 0.5% by mass or less. The nitrogen content can be measured according to JIS M8813:2004.

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

[Mixing process]
Next, the powder obtained in the above-mentioned pulverization process is mixed with either fuel oil or water, or both, to obtain a slurry fuel (mixing process). 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).

In the mixing process, one or both of a BOM and a BWM can be produced. In other words, the mixing process includes one or both of a process of mixing the powder with fuel oil to produce a BOM and a process of mixing the powder with water to produce a BWM.

The mixing device used for the mixing is not particularly limited, and any stirrer 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, first, only the powder is pulverized by the pulverizer, and then fuel oil or water is added and mixed. In other words, the pulverizer may be used to perform the pulverization process and the mixing process continuously. In this case, the pulverizer serves as both the pulverization device and the mixing device.

The above 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.

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 reduced more sufficiently, and _CO2 can be reduced more effectively.

The viscosity of the slurry fuel is not particularly limited. However, lowering the viscosity improves the fluidity of the slurry fuel, which in turn improves the ease of handling and transporting 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.

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 with rotor #1 manufactured by Toki Sangyo can be used as the viscometer.

The above-mentioned slurry fuel may be thixotropic or rheopexic, but is preferably thixotropic.

(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, it is preferable that the fuel oil is a highly distilled product derived from crude oil. More preferable are liquid fuel oils such as light oil, heavy oil, kerosene, naphtha, gasoline, and jet fuel oil, and even more preferable are light oil, heavy oil, and kerosene. Examples of the heavy oil include heavy oil A, heavy oil B, and heavy oil C.

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

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, it is 100 mPa·s or less, and particularly preferably, it is 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. On the other hand, the lower limit of the viscosity of the fuel oil is not limited, but it may typically be 1 mPa·s or more, or 5 mPa·s or more.

On the other hand, when the powder is mixed with water to make 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 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 slurry fuel.

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

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 to drive the internal combustion engine. This is because when the slurry fuel is burned, the water evaporates and the volume expands.

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

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

(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 preferable to use a dispersant.

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 increasing 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.

As the dispersant, any dispersant can be used without any particular limitation. As the dispersant, 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.

(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; various sulfonic acid-based dispersants having a sulfonic acid group in the molecule such as nonylphenyl sulfonate.

(ii) As described in JP-B-59-18338 and JP-A-7-223852, copolymers obtained from polyalkylene glycol mono(meth)acrylic acid ester monomers, (meth)acrylic acid monomers, and monomers copolymerizable with these monomers; as described in JP-A-10-236858, JP-A-2001-220417, JP-A-2002-121055, and JP-A-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.

(iii) Polyvinylpyrrolidone.

(iv) polyacrylic acid.

(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, phosphate monoester monomers, and phosphate diester monomers; 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, dispersants having an aromatic triazine structural unit, a polyalkylene glycol structural unit, and a phosphate ester structural unit; and various other phosphate-based dispersants.

(vi) Anionic surfactants such as alkyl sulfate ester salts, higher alcohol sulfate ester salts, nonionic ether sulfate ester salts, olefin sulfate ester salts, polyoxyethylene alkyl (alkylphenol) sulfate ester salts, alkyl aryl sulfonates, dibasic acid ester sulfonates, alkyl benzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate ester salts, and acylsarcosinates.

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

(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, alkyl trimethyl ammonium chlorides, alkyl dimethyl benzyl ammonium chlorides, polyoxyethylene fatty acid esters, fatty alcohol polyoxyethylene ethers, polyhydric alcohol fatty acid esters, and fatty acid ethanolamides,

(ix) Amphoteric surfactants such as alkyl betaines.

Among them, 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). In addition, this polycarboxylic acid-based dispersant is particularly effective as a dispersant when mixed with water.

(In the formula, R ¹ , R ² and R ³ are the same or different and represent a hydrogen atom or a methyl group. R 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.)

When ^R4 in the above formula (1) 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.

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), cinnamyl groups (Ph-CH=CHCH ₂ - group), 1-benzocyclobutenyl group, 1,2,3,4-tetrahydronaphthyl group and other aromatic hydrocarbon groups are preferred.

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

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. This means that the n oxyalkylene groups of R ⁵ O present in the polyalkylene glycol may all be the same or different.

The number of carbon atoms in the oxyalkylene group is preferably 2 to 18. More preferably, it is 2 to 12, even more preferably 2 to 8, and most preferably 2 to 4.

In the above formula (1), the oxyalkylene group represented by R ⁵ 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.

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, but 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. (Meth)acrylic acid, maleic acid, and salts thereof are preferred.

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

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

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

When the powder is mixed with fuel oil to produce 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.

On the other hand, when the powder is mixed with water to form 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. If the weight average molecular weight is 1,000 or more, foaming during dispersion can be more sufficiently suppressed.

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

The weight average molecular weight of the dispersant can be measured using gel permeation chromatography (GPC) in terms of standard polystyrene.

The above-mentioned slurry fuel may contain other components in addition to the powder and fuel oil or water. The other components are not particularly limited, but 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 can be added. In particular, in the case of BOM, stabilizers, separation reducing agents, thickeners, viscosity reducing agents, biofuels, ignition agents, cetane number improvers, lubricants, etc. can be suitably added. Also, in the case of BWM, stabilizers, thickeners, viscosity reducing agents, ignition agents, organic solvents, water retention agents, lubricants, etc. can be suitably added.

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

The stabilizer is not particularly limited, but for example, in the case of BOM, examples include polyalkylene oxide adducts of alcohols. Of these, polyalkylene oxide adducts of glycerin are preferred. In the case of BWM, examples include ammonia, sodium hydroxide, and amines. Of these, ammonia is preferred.

The thickener is not particularly limited, but examples include polysaccharides, polyacrylamides, polyalkylene oxides, polyacrylic acid and its salts, polyvinyl alcohol, etc.

The viscosity reducing agent is not particularly limited, but examples include glycol monoethers, glycol diethers, phenyl glycol ethers, benzyl glycols, etc.

The above-mentioned ignition agent is not particularly limited, but examples include heavy oil, light oil, bioalcohol, etc. Among them, biobutanol, biopropanol, and bioethanol are preferred.

The organic solvent is not particularly limited, but examples 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.

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

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 according to this embodiment further includes 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) and (7).
(6) First hydrogen production process (7) Second hydrogen production process

[First hydrogen production process]
In the liquefaction step, gaseous components obtained by pyrolysis of plant biomass are liquefied, but some components (off-gas) remain in gaseous form 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 , 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 utilized more effectively.

[Second hydrogen production process]
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, _CO2 , _H2O , _H2 , methane, and other gases that are produced by hydrolysis of carboxyl groups and the like during the hydrothermal treatment. Therefore, by producing hydrogen from this off-gas, plant biomass can be used more effectively.

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.

The first hydrogen production process and the second hydrogen production process may be carried out separately or together. That is, hydrogen production from the first off-gas and hydrogen production from the second off-gas may be carried out 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.

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

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

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

The green hydrogen obtained in this way can be used for a variety of purposes, including as fuel for fuel cells and rocket fuel.

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

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 the present invention is not limited to the following examples.

Example 1
First, tests were conducted to obtain solid components (carbonized material) and liquid components by pyrolyzing plant biomass at 400°C (Test Nos. 1 to 3). Specifically, each of the three types of plant biomass shown in Table 1 was pyrolyzed at atmospheric pressure and at a temperature of 400°C. A rotary kiln-type carbonization furnace with a rated processing capacity of 20 kg/h and an internal baffle plate was used for the pyrolysis. The processing time (the time from loading into the carbonization furnace to discharging) was about 60 minutes. The weight of the plant biomass subjected to pyrolysis (amount of raw material supplied) 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.

After pyrolysis was carried out under the above conditions, the remaining solid components were recovered as they were. The gas components generated by pyrolysis were liquefied by cooling to atmospheric temperature (about 30°C) using a scrubber, and were recovered as liquid components. The 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) × 100

Furthermore, the ash, 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 analysis results are shown in Table 2. These analysis results are measurements on an anhydrous basis. For reference, the fuel ratio (= fixed carbon/volatile matter) is also shown in Table 2.

The results shown in Table 1 show that by pyrolyzing under the conditions of the present invention, solid and liquid components can be appropriately recovered regardless of the type of plant biomass used. Furthermore, as shown in Table 2, all of the solid components obtained had sufficient heating value. Furthermore, all of the solid components had an ash content of 15 mass% or less, a nitrogen content of 1.0 mass% or less, and a sulfur content of 0.05 mass% or less.

Example 2
Next, tests were conducted to obtain solid components (charcoal) and liquid components 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. The analysis results of the obtained solid components are shown in Table 3.

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

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 was subjected to the oxygen reduction treatment under two conditions to produce liquid fuel. In the first condition, the liquid component was placed in a pail can and aged at room temperature and atmospheric pressure for one and a half years (No. 1-2). In 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 about 300°C and a pressure of about 27 MPa.

After the above-mentioned oxygen reduction process, elemental analysis was performed on the obtained fuel 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 liquid components that were not subjected to oxygen reduction process are also shown in Table 4 (No. 1-1).

The results shown in Table 4 show that oxygen reduction treatment can reduce the amount of oxygen to approximately 20%.

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

Example 4
Next, slurry fuels (BOM) were produced using the solid component (carbide) obtained in No. 1 of Example 1 above (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 1 hour. After that, filtration was performed using a 200 mesh wire screen to obtain slurry fuels. Nos. 10 to 12 each had the following composition.
No. 10: 30% by mass of carbide powder, balance A heavy oil No. 11: 30% by mass of carbide powder, 3 parts by mass of dispersant (per 100 parts by mass of carbide powder), balance A heavy oil No. 12: 15% by mass of carbide powder, balance A heavy oil

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 normal heavy oil A without any carbonized matter 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.

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

A polycarboxylic acid-based dispersant was used as the dispersant. The polycarboxylic acid-based dispersant is 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 powder.

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.

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.

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 LabNext), and then a Pulvis PV-150 (manufactured by Hosokawa Micron Corporation) was used as a fine pulverizer, and the operating conditions were adjusted within the following ranges to obtain carbonized pulverized material with the average particle size shown in Table 6 (Nos. 30 to 36). However, in No. 36, after the coarse pulverization, the material was classified using a sieve with 20 μm openings to obtain a powder with an average particle size of 20.2 μm.

The average circularity of the carbonized pulverized products having 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 grinding mill>
・Media: Stainless steel beads 3mm, 4.5kg used ・Raw material input speed: 5-20g/min
・Crusher 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

Furthermore, the obtained powder was slowly added to diesel 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 obtained slurry fuel is also shown in Table 6. The viscosity was measured by the method described above.

(Example 7)
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.

The same powder as used in Example 6 was dispersed in water to create a slurry fuel (BWM). A polycarboxylic acid-based dispersant was used as the dispersant. The polycarboxylic acid-based dispersant is 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 powder.

The powder content in the slurry fuel was as shown in Table 7. The viscosity of the resulting slurry fuel is also shown in Table 7. The viscosity was measured using the method described above.

Claims (7)

a pyrolysis step of pyrolyzing the plant biomass at 350 to 430°C to obtain a gas component and a solid component;
a liquefaction step of cooling the gas component to obtain a liquid component;
an oxygen reducing treatment step for reducing oxygen in the liquid component to obtain a liquid fuel;
a grinding step of grinding the solid component to obtain a powder;
A mixing step of mixing the powder with either or both of fuel oil and water to obtain a slurry fuel. The fuel production method according to claim 1, further comprising a first hydrogen production process for producing hydrogen from a first off-gas that was not liquefied in the liquefaction process. The fuel production method according to claim 1 or 2, further comprising a second hydrogen production process for producing hydrogen from a second off-gas by-produced in the oxygen reduction process. The 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 the volume-based particle size distribution is within ±10% of the average particle size. A pyrolysis device for pyrolyzing plant biomass at 350 to 430°C to obtain gaseous and solid components;
a liquefaction device for cooling the gas component to obtain a liquid component;
an oxygen reducing treatment device for reducing oxygen in the liquid component to obtain a liquid fuel;
a grinding device for grinding the solid component to obtain a powder;
and a mixer for mixing the powder with fuel oil and/or water to obtain a slurry fuel. The fuel production device according to claim 5, further comprising a first hydrogen production device that produces hydrogen from a first off-gas that was not liquefied by the liquefaction device. The fuel production device according to claim 5 or 6, further comprising a second hydrogen production device that produces hydrogen from a second off-gas by-produced in the oxygen reduction treatment device.

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