Solid fuel, method for firing solid fuel, and method for producing solid fuel

Abstract

To provide a solid fuel that contains biomass while suppressing fouling. [Solution] The present invention provides a solid fuel comprising biomass char and pulverized coal, wherein, when the total amount of the biomass char and pulverized coal in an oven-dry state is taken as 100% by mass, the biomass char content is 3 to 90% by mass, and the pulverized coal content is 10 to 97% by mass, and in the biomass char, the mannose content as constituent sugars is 2.0 to 12.0% by mass, the xylose content is 0.3 to 10.0% by mass, the arabinose content is 1.0% by mass or less, and the glucose content is 40.0 to 55.0% by mass, and the ash content of the pulverized coal is 20 to 40% by mass on an oven-dry basis.

Description

[Technical Field]

[0001] This disclosure relates to solid fuels, methods for firing solid fuels, and methods for manufacturing solid fuels. [Background technology]

[0002] Biomass solid fuels using biomass have been known conventionally. Biomass solid fuels are expected to be an alternative to fossil fuels. Patent Document 1 discloses a biomass solid fuel with reduced chemical oxygen demand (COD) of wastewater. Patent Document 2 discloses a method for producing a biomass solid fuel with reduced self-heating properties while suppressing decay during production. Patent Document 3 discloses a method for producing a biomass solid fuel with excellent water resistance using biomass raw materials that are easy to cultivate and harvest on a commercial scale. Non-Patent Documents 1 and 2 describe methods for analyzing the constituent sugars of biomass.

[0003] Methods are being investigated to suppress slagging and fouling caused by ash generated when burning biomass solid fuel. Slagging refers to the formation of an ash layer when molten ash particles in the furnace collide with the furnace wall and adhere to it. Fouling refers to the formation of an ash layer when molten or vaporized low-melting-point ash adheres to heat transfer tubes or heat exchangers. When slagging or fouling occurs, problems such as boiler deterioration and a decrease in heat exchange efficiency occur. Patent document 4 discloses a combustion apparatus and combustion method that can burn biomass while suppressing slagging. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2016 / 056608 [Patent Document 2] Japanese Patent Publication No. 2020-033396 [Patent Document 3] U.S. Patent Application Publication No. 2022 / 0306958 [Patent Document 4] Japanese Patent Publication No. 2004-0354031 [Non-patent literature]

[0005] [Non-Patent Document 1] A. Sluiter et. al., “Determination of Structural Carbohydrates and Lignin in Biomass”, [online], pp. 3-8, August 2012, National Renewable Energy Laboratory, [Retrieved March 7, 2023], Internet<URL:https: / / www.nrel.gov / docs / gen / fy13 / 42618.pdf> [Non-Patent Document 2] Momoko Kondo et al., "Initiatives for Contract Analysis of Constituent Sugars in Woody Biomass," Biomass Section, Japan Energy Society, Proceedings of the 12th Biomass Science Conference, January 2017, pp. 159-160. [Overview of the project] [Problems that the invention aims to solve]

[0006] The ash contained in biomass solid fuel has a softening point of 600-1100°C, which is lower than the softening point of ash contained in coal. Therefore, when burning biomass solid fuel in a coal combustion facility, simply replacing coal with biomass solid fuel or burning it mixed with coal can cause the ash contained in the biomass solid fuel to melt or vaporize, resulting in fouling. This disclosure provides a solid fuel that contains biomass but can suppress fouling, a method for firing the solid fuel, and a method for manufacturing the solid fuel. [Means for solving the problem]

[0007] One aspect of this disclosure is a solid fuel comprising biomass char and pulverized coal, wherein, when the total amount of the biomass char and pulverized coal in an oven-dry state is taken as 100% by mass, the content of the biomass char is 3 to 90% by mass, and the content of the pulverized coal is 10 to 97% by mass, and in the biomass char, the content of mannose as a constituent sugar is 2.0 to 12.0% by mass, the content of xylose is 0.3 to 10.0% by mass, the content of arabinose is 1.0% by mass or less, and the content of glucose is 40.0 to 55.0% by mass, and the ash content of the pulverized coal is 20 to 40% by mass on an oven-dry basis.

[0008] The above solid fuel contains biomass char containing predetermined amounts of mannose, xylose, arabinose, and glucose as constituent sugars, and pulverized coal with a relatively high ash content, in a predetermined mass ratio. Biomass char is known to be more prone to fouling than pulverized coal. On the other hand, pulverized coal alone cannot be expected to reduce CO2 emissions. However, by deliberately selecting low-grade pulverized coal with a high ash content and low calorific value, and combining it with biomass char in an appropriate range, the above solid fuel can effectively utilize low-grade coal, suppress fouling, and also achieve a CO2 reduction effect.

[0009] One aspect of this disclosure provides a method for calcining a solid fuel, which includes the step of calcining the solid fuel described above.

[0010] The above method for firing solid fuel involves firing a solid fuel containing a predetermined mass ratio of biomass char containing predetermined amounts of mannose, xylose, arabinose, and glucose as constituent sugars, and pulverized coal containing a predetermined amount of ash. Such a solid fuel has a sufficiently reduced amount of ash, which is easily melted at low temperatures, and can suppress the melting of ash during firing. Therefore, fouling can be suppressed.

[0011] One aspect of the present disclosure includes a step of mixing biomass carbide and pulverized coal to obtain a mixture. In the mixture, when the total amount in the absolutely dry state of the biomass carbide and the pulverized coal is 100% by mass, the content of the biomass carbide is 3 to 90% by mass, and the content of the pulverized coal is 10 to 97% by mass. In the biomass carbide, the content rate of mannose contained as a constituent sugar is 2.0 to 12.0% by mass, the content rate of xylose is 0.3 to 10.0% by mass, the content rate of arabinose is 1.0% by mass or less, and the content rate of glucose is 40.0 to 55.0% by mass. The ash content in the pulverized coal is 20 to 40% by mass on an absolutely dry basis. A method for manufacturing a solid fuel is provided.

[0012] The method for manufacturing the solid fuel described above has a step of mixing biomass carbide containing a predetermined amount of mannose, xylose, arabinose, and glucose as constituent sugars and pulverized coal containing a predetermined amount of ash at a predetermined mass ratio to obtain a mixture. The solid fuel thus obtained has sufficiently reduced ash that is easily melted at low temperatures, and it is possible to suppress the melting of ash when fired. Therefore, the solid fuel obtained by the above manufacturing method can suppress fouling.

Effects of the Invention

[0013] The present disclosure can provide a solid fuel capable of suppressing fouling while containing biomass, a method for firing the solid fuel, and a method for manufacturing the solid fuel.

Brief Description of the Drawings

[0014] [Figure 1] It is a graph showing the relationship between temperature and melt ratio in Examples 1 to 3, Comparative Example 1, and Comparative Example 2. [Figure 2] It is a graph showing the relationship between temperature and mass (TG curve) in Examples 1 to 3, Comparative Example 1, and Comparative Example 2. [Figure 3] It is a graph showing the relationship between temperature and mass change amount (DTG curve) in Examples 1 to 3, Comparative Example 1, and Comparative Example 2. [Modes for carrying out the invention]

[0015] Embodiments of this disclosure are described below. However, the following embodiments are illustrative for the purpose of illustrating this disclosure and are not intended to limit this disclosure to the following. The upper or lower limits of numerical ranges explicitly stated in this disclosure may be replaced with any of the values ​​shown in the examples. Furthermore, the upper and lower limits described individually may be combined in any way. Unless otherwise specified, the materials or components illustrated in this disclosure may be used individually or in combination of two or more. The symbol "~" used in numerical ranges indicates a numerical range that includes the upper and lower limits. For example, "X~Y" indicates a numerical range of "X or greater and Y or less".

[0016] [Solid fuel] In one embodiment, the solid fuel contains biomass char and pulverized coal, and when the total amount of biomass char and pulverized coal in an oven-dry state is taken as 100, the biomass char content is 3 to 90% by mass and the pulverized coal content is 10 to 97% by mass.

[0017] In solid fuel, biomass char and pulverized coal can coexist in the aforementioned proportions. For example, the fine particles obtained by finely grinding each of them may be mixed in the above-mentioned proportions to form a powder, or the powder may be formed into briquettes. Alternatively, the solid fuel may be a mixture of unground biomass char pellets and pulverized coal in the above-mentioned proportions. Furthermore, the solid fuel may be in the form of pellets containing biomass char and pulverized coal in the above-mentioned proportions, or it may be in the form of bags in flexible containers, or it may be piled up in a stockyard. In other words, when burning the solid fuel in a boiler, it is sufficient that the biomass char and pulverized coal can be co-fired in the above-mentioned proportions. Note that the solid fuel may contain components other than biomass char and pulverized coal, or it may consist only of biomass char and pulverized coal.

[0018] In this disclosure, "absolutely dry state" means the state after the object to be measured (e.g., biomass char, pulverized coal, etc.) has been heated at 107°C for 4 hours or more and has reached a constant weight.

[0019] The inclusion of biomass char in solid fuel can improve its ignition properties. From the viewpoint of further improving the ignition properties of solid fuel, the biomass char content, when the total amount of biomass char and pulverized coal in a completely dry state is taken as 100% by mass, may be 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more. Furthermore, from the viewpoint of reducing the amount of ash with a low softening point contained in the solid fuel and further suppressing fouling, the biomass char content, when the total amount of biomass char and pulverized coal in a completely dry state is taken as 100% by mass, may be 80% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less.

[0020] The inclusion of pulverized coal in solid fuels improves the sustainability of combustion and further suppresses fouling. From the viewpoint of improving the sustainability of combustion and further suppressing fouling, the pulverized coal content when the total amount of biomass char and pulverized coal in a dry state is taken as 100% by mass may be 20% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more. From the viewpoint of reducing the amount of fossil fuels used and suppressing the environmental burden, the pulverized coal content when the total amount of biomass char and pulverized coal in a dry state is taken as 100% by mass may be 95% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less.

[0021] The solid fuel has a bulk density of 600-900 kg / m³ according to JIS Z 8807:2012. 3 , 650~900 kg / m 3 , or 700-900 kg / m 3 That's fine.

[0022] The fuel ratio (fixed carbon / volatile matter) of solid fuels may be 0.30 to 2.50, 0.40 to 2.20, or 0.60 to 2.10, from the viewpoint of further improving the combustibility of the solid fuel. The fixed carbon and volatile matter of solid fuels can be measured in accordance with JIS M 8812:2006. The fixed carbon of solid fuels may be 25 to 68% by mass, 30 to 65% by mass, or 40 to 60% by mass. The volatile matter of solid fuels may be 30 to 70% by mass, or 35 to 60% by mass. By having the volatile matter and fixed carbon of solid fuels within the above ranges, the combustibility of the solid fuel can be further suppressed.

[0023] The higher heating value of a solid fuel in its dry state may be 21,000 to 25,000 kJ / kg, 22,000 to 25,000 kJ / kg, or 23,000 to 25,000 kJ / kg. Having the higher heating value of the solid fuel in its dry state within the above range can further improve its combustibility. The higher heating value of the solid fuel in its dry state can be measured in accordance with JIS M 8814:2003.

[0024] The ash content of the solid fuel may be 7-26% by mass, 7-23% by mass, or 10-22% by mass in an oven-dry state. By keeping the ash content of the solid fuel within the above range, fouling can be suppressed even with low-grade solid fuel that contains a certain amount of ash.

[0025] Fouling refers to the adhesion of molten or vaporized low-melting-point ash to heat transfer tubes or heat exchangers, forming an ash deposit layer. In this disclosure, fouling can be evaluated by simulation calculated using the thermodynamic calculation software "FactSage Ver. 8.1". Specifically, the proportions of chemical species that exist stably in chemical equilibrium, solid solutions (such as oxides generated when solid fuels are burned), and melts (molten solid solutions) in the ash composition of a sample were simulated between 500°C and 1700°C, and the proportion of melts at 1100°C was used as an indicator of fouling. The atmospheric conditions for the simulation may be O2 concentration of 21 vol%, CO2 concentration of 0.1 vol%, and pressure of 1 atm. Furthermore, the ash composition in the sample can be determined by ash composition measurement as described later.

[0026] The melting percentage at 1100°C may be 35% by mass or less, 30% by mass or less, 25% by mass or less, or 20% by mass or less. The smaller the melting percentage at 1100°C, the less likely the ash is to melt at low temperatures, preventing the ash particles from bonding together due to the melt and thus suppressing fouling. The melting percentage at 1100°C may be 5% by mass or more. For example, the melting percentage at 1100°C may be 5-35% by mass, 5-30% by mass, 5-25% by mass, or 5-20% by mass.

[0027] The fuel characteristics of solid fuels can be evaluated by their ignition properties and combustion duration. The ignition temperature can be determined by measuring the point at which the mass rapidly decreases using differential thermal-thermogravimetric analysis (TG-DTA). Biomass char has a lower ignition temperature and burns out more quickly than pulverized coal. On the other hand, pulverized coal has a higher ignition temperature and burns out more quickly than biomass char. Therefore, when biomass char and pulverized coal are co-fired, the biomass char ignites first at a low temperature, and then the pulverized coal ignites at a high temperature. Thus, a solid fuel mixture of biomass char and pulverized coal can achieve both good ignition properties and combustion duration.

[0028] In solid fuel, the peak mass change when biomass char is ignited may be 100 μg / (min·mg) or more, or 130 μg / (min·mg) or more. Having the peak mass change within the above range improves the ignition properties of the solid fuel. In solid fuel, the peak mass change when biomass char is ignited may be 1000 μg / (min·mg) or less, or 800 μg / (min·mg) or less. Having the peak mass change within the above range increases the pulverized coal content in the solid fuel, improving the combustion sustainability of the solid fuel. TG-DTA can be performed, for example, by heating with a heating rate of 20°C / min using "STA7300" (manufactured by Hitachi High-Tech Science Corporation). Ignition of biomass char can be confirmed by a rapid mass change in the 350°C to 380°C range.

[0029] In the case of a solid fuel, when heated from room temperature at a heating rate of 20°C / min, the temperature at which the mass change after ignition is 20 μg / (min·mg) or less may be 520°C or higher. Since the temperature at which the mass change after ignition is 20 μg / (min·mg) or less is a temperature at which the mass hardly changes even when heated, in this disclosure this temperature can be defined as the "burnout temperature" of the solid fuel. A burnout temperature of 520°C or higher can improve the combustion sustainability of the solid fuel. From the viewpoint of further improving the combustion sustainability of the solid fuel, the burnout temperature may be 530°C or higher, 540°C or higher, or 550°C or higher. The burnout temperature may also be 600°C or lower. The burnout temperature may be, for example, 520~600°C, 530~600°C, or 550~600°C. The burnout temperature can be measured by the TG-DTA described above.

[0030] The CO2 reduction rate for solid fuels may be 5% or more, 10% or more, 20% or more, 40% or more, or 60% or more. By keeping the CO2 reduction rate within the above range, the environmental burden caused by the use of fossil fuels can be reduced. Furthermore, the CO2 reduction rate for solid fuels may be 90% or less. For example, the CO2 reduction rate for solid fuels may be 5-90%, 10-90%, 20-90%, 40-90%, or 60-90%. CO2 emissions from burning biomass fuel are not included in the calculations for periodic reports based on Article 16, Paragraph 1, Article 28, Paragraph 1, and Article 40, Paragraph 1 of the Act on Rationalization of Energy Use and Transition to Non-Fossil Energy. Therefore, for example, when biomass fuel is used in a coal-fired boiler, the amount of coal (pulverized coal) used that produces the same calorific value is reduced, thereby reducing the energy-derived CO2 emissions from the total fuel input to the boiler. Therefore, for example, the CO2 reduction rate can be calculated using the following equation (1). In equation (1), the lower heating value is the heating value obtained by subtracting the latent heat of vaporization of water from the higher heating value. [CO2 reduction rate (%)] = [1 - (weight percentage of pulverized coal × lower heating value of pulverized coal (considering moisture content)) / (weight percentage of pulverized coal × lower heating value of pulverized coal (considering moisture content) + weight percentage of biomass × lower heating value of biomass (considering moisture content))] × 100 (1)

[0031] [Fine pulverized coal] In this disclosure, pulverized coal may be obtained by crushing dried coal into a fine powder, or by sieving coal extracted from a coal mine and collecting the fine powder portion. By including pulverized coal in the solid fuel, the amount of low-melting-point ash is reduced, which can suppress fouling during the combustion of the solid fuel.

[0032] In solid fuels, the ash content of pulverized coal is 20-40% by mass in an oven-dry state. Having the ash content within this range suppresses fouling even when using low-grade, inexpensive pulverized coal that contains a certain amount of ash. From the viewpoint of further suppressing fouling, the ash content of pulverized coal may be 30% by mass or less in an oven-dry state. From the viewpoint of further reducing the cost of pulverized coal, the ash content of pulverized coal may be 25% by mass or more in an oven-dry state. For example, the ash content of pulverized coal may be 25-30% by mass in an oven-dry state.

[0033] The moisture content of pulverized coal may be 2.0-5.0% by mass, 2.5-4.5% by mass, or 3.0-4.0% by mass. Having a moisture content within these ranges can further improve the combustibility of the solid fuel. The moisture content and ash content of pulverized coal can be measured in accordance with JIS M 8812:2006.

[0034] The softening point (IT), melting point (HT), and flow point (FT) of the ash contained in pulverized coal may each be 1500°C or higher, and the temperature at which the height of the test pipe equals the width of the test pipe (ST) when measuring IT, HT, and FT may also be 1500°C or higher. By having the IT, HT, FT, and ST of the ash contained in pulverized coal within the above range, it is possible to prevent the ash from melting at low temperatures when heated, and to further suppress fouling when burning solid fuel. Note that the IT, HT, FT, and ST of the ash contained in pulverized coal may each be 2000°C or lower. For example, the IT, HT, FT, and ST of the ash contained in pulverized coal may each be between 1500 and 2000°C.

[0035] The IT, HT, FT, and ST of ash contained in pulverized coal can be measured in accordance with JIS M8801:2004. Specifically, a 20-30g sample is used to create a triangular pyramid test sample with a height of 8mm, a base length of 2.7mm on two sides and 3mm on the other side, and one of the faces being 3mm long. The test sample is then heated in a furnace, and the melting of the test pyramid is observed.

[0036] The ash composition of pulverized coal may contain at least one selected from the group consisting of SiO2, Fe2O3, Al2O3, CaO, MgO, SO3, P2O5, TiO2, Na2O, K2O, V2O5, NiO2, and MnO. The content of each component in the ash composition of pulverized coal can be determined by the method described in the examples.

[0037] In pulverized coal, the ash composition may be such that K2O / (Al2O3+SiO2) is 0.05 or less, CaO / (Al2O3+SiO2) is 0.05 or less, and MgO / (Al2O3+SiO2) is 0.05 or less. Since K2O, CaO, and MgO are low-melting-point ashes, having potassium aluminosilicate [K2O / (Al2O2+SiO2)], calcium aluminosilicate [CaO / (Al2O3+SiO2)], and magnesium aluminosilicate [MgO / (Al2O3+SiO2)] within the above ranges reduces the content of low-melting-point ash in the solid fuel, thereby preventing the ash from melting at low temperatures and suppressing fouling.

[0038] From the viewpoint of further suppressing fouling, the K2O / (Al2O3+SiO2) ratio may be 0.04 or less, 0.03 or less, or 0.02 or less. From the viewpoint of further suppressing fouling, the CaO / (Al2O3+SiO2) ratio may be 0.03 or less, or 0.02 or less. From the viewpoint of further suppressing fouling, the MgO / (Al2O3+SiO2) ratio may be 0.03 or less, or 0.02 or less.

[0039] The Na+K content in pulverized coal may be 500-2000 ppm by mass, 750-1700 ppm by mass, or 900-1500 ppm by mass. The Na+K content (ppm by mass) can be determined using the Na2O and K2O content in the ash composition, as shown in formula (2) below. Note that the moisture content and ash content in formula (2) refer to measurements under normal conditions, not under completely dry conditions. Na + K = (Na2O × 46 / 62 + K2O × 78 / 96) × (ash content) / (1 - moisture content / 100) × 100 (2)

[0040] The bulk density of the fine powder coal, based on JIS Z 8807:2012, may be 500 - 1500 kg / m 3 650 - 1200 kg / m 3 or 800 - 1000 kg / m 3

[0041] From the perspective of further improving the combustibility of solid fuels, the fuel ratio (fixed carbon / volatile matter) in the fine powder coal may be 1.0 - 3.0, 1.5 - 2.8, or 2.0 - 2.7. The fixed carbon and volatile matter of the fine powder coal can be measured in accordance with JIS M 8812:2006. The fixed carbon in the fine powder coal may be 60 - 80% by mass, 65 - 75% by mass, or 68 - 72% by mass. The volatile matter in the fine powder coal may be 10 - 30% by mass, 15 - 30% by mass, 20 - 28% by mass, or 25 - 28% by mass. By the volatile matter and fixed carbon of the fine powder coal being within the above ranges, the combustibility of the fine powder coal can be further suppressed.

[0042] The gross calorific value of the fine powder coal may be 20000 - 30000 kJ / kg, 22000 - 28000 kJ / kg, or 24000 - 26000 kJ / kg in the absolutely dry state. By the gross calorific value of the fine powder coal in the absolutely dry state being within the above range, the combustibility of the solid fuel can be further improved. The gross calorific value of the fine powder coal in the absolutely dry state can be measured in accordance with JIS M 8814:2003.

[0043] The true specific gravity of the fine powder coal may be 1.0 - 2.0 g / mL, 1.2 - 1.8 g / mL, or 1.4 - 1.7 g / mL. The true specific gravity of the fine powder coal can be measured, for example, using an ultra pycnometer.

[0044] The BET specific surface area of the fine powder coal is 3 - 12 m 2 / g, 5 - 10 m 2 / g, or 5 - 8 m 2 ​It may also be / g. The BET specific surface area of ​​pulverized coal can be measured, for example, by a constant volume method using nitrogen gas adsorption with a specific surface area / pore size analyzer.

[0045] The pore volume of pulverized coal may be 0.04-0.15 mL / g, 0.06-0.12 mL / g, or 0.07-0.10 mL / g. The pore volume of pulverized coal can be measured, for example, by the mercury injection method using a fully automated pore distribution analyzer.

[0046] The specific surface area of ​​pulverized coal is 15-50 m². 2 / g, 20-40m 2 / g, or 25-35m 2 It may also be / g. The specific surface area of ​​pulverized coal can be measured, for example, by the mercury injection method using a fully automated pore size distribution analyzer.

[0047] The median diameter of the pulverized coal may be 0.010 to 0.10 μm, 0.015 to 0.050 μm, or 0.020 to 0.040 μm. Having a median diameter within the above range allows for sufficient mixing with biomass char and enables adequate co-firing of the biomass char and pulverized coal. The median diameter of the pulverized coal can be measured, for example, by a mercury injection method using a fully automated pore size analyzer.

[0048] [Biomass char] In this disclosure, biomass char may refer to biomass that has been heated and carbonized. Such biomass char has a relatively low content of the persistently decomposable mannose, so the decomposition of polysaccharides and constituent sugars by heating during production proceeds sufficiently. Therefore, as polysaccharides and constituent sugars are decomposed, substances that suppress powdering are produced, and the powdering rate can be reduced. Such biomass char has excellent yield. In the biomass char, the content of mannose contained as a constituent sugar is 2.0 to 12.0% by mass. The mannose content may be, for example, 4.0 to 10.0% by mass, or 6.0 to 9.0% by mass.

[0049] In biomass char, the xylose content as a constituent sugar is 0.3 to 10.0% by mass. In biomass char with a xylose content within the above range, the xylose is sufficiently decomposed by heating during manufacturing, and the xylose is transformed into a substance that suppresses powdering, thus suppressing the powdering of the biomass char. From the viewpoint of further suppressing the powdering of biomass char while increasing the yield, the xylose content as a constituent sugar may be 1.0 to 8.0% by mass, 2.0 to 7.0% by mass, or 2.5 to 5.0% by mass.

[0050] In biomass char, the content of arabinose as a constituent sugar is 1.0% by mass or less. The content of arabinose as a constituent sugar may be 0.5% by mass or less.

[0051] In biomass char, the glucose content as a constituent sugar is 40.0 to 55.0% by mass. The glucose content as a constituent sugar may also be 45.0 to 50.0% by mass.

[0052] In biomass char, the galactose content as a constituent sugar may be 0.5 to 2.0% by mass, or 1.0 to 1.8% by mass.

[0053] The type of biomass is not particularly limited, as long as the biomass char contains 2.0 to 12.0% by mass of mannose, 0.3 to 10.0% by mass of xylose, 1.0% or less of arabinose, and 40.0 to 55.0% by mass of glucose as constituent sugars.

[0054] Examples of biomass used as raw material for biomass carbon include bagasse, acacia, conifers, rubber trees, eucalyptus, meranti, teak, oil palm trunks, empty palm fruit clusters, sorghum, and Napier grass. Among these, conifers are preferred, and examples of conifers include Japanese cedar, cypress, larch, hinoki cypress, fir, spruce, radiata pine, Scots pine, and hemlock. One or more of these may be used in combination. For example, it is preferable to include 10-50% by mass or 20-40% by mass of spruce, 30-60% by mass or 40-50% by mass of pine, and 10-40% by mass or 20-30% by mass of fir. The biomass carbon may be obtained by heating these biomass materials. In other words, the biomass char may be, for example, bagasse char, acacia char, coniferous tree char, rubber tree char, eucalyptus char, meranti char, teak char, oil palm trunk char, empty palm fruit cluster char, sorghum char, and Napier grass char.

[0055] Monosaccharides such as mannose, xylose, arabinose, glucose, and galactose constitute the polysaccharides contained in biomass char. Because polysaccharides have large molecular weights, their content cannot be directly measured by analytical instruments. Therefore, in this disclosure, the polysaccharide content is determined, for example, by measuring the content of constituent sugars obtained by hydrolyzing polysaccharides in a sample with acid using HPLC or GC, and multiplying it by a polysaccharide conversion factor that takes into account the over-decomposition of constituent sugars. The analytical method for constituent sugars in biomass can be measured, for example, by the method described in Non-Patent Document 1 or Non-Patent Document 2. In this disclosure, the content of each monosaccharide as a constituent sugar means the content of each monosaccharide detected by the method described in Non-Patent Document 1 or Non-Patent Document 2, and does not necessarily specify that it exists as a monosaccharide in the biomass char.

[0056] The content of constituent sugars can be determined by, for example, adding 3 mL of 72% by mass sulfuric acid to 0.3 g of the biomass char to be measured, reacting at 30°C for 1 hour, filtering the reaction solution, and analyzing the filtrate by HPLC or GC-MS. GC-MS is preferred due to its versatility and excellent selectivity. The content of constituent sugars can be specifically determined by the method described in the examples.

[0057] The above analytical method can measure the content of constituent sugars such as glucose, galactose, arabinose, xylose, and mannose as constituent sugars of polysaccharides. By multiplying the measurement result by the polysaccharide conversion factor for each constituent sugar, the content of polysaccharides containing each constituent sugar can be considered. Examples of polysaccharides include glucan, galactan, arabinan, xylan, and mannan. Biomass char may contain at least one of such polysaccharides. For example, biomass char may contain glucan and xylan. On the other hand, biomass char may not contain mannan, arabinan, and galactan. In this disclosure, "not containing constituent sugars or polysaccharides" means that they are below the detection limit.

[0058] The biomass used as a raw material may contain the polysaccharides mentioned above. Furthermore, a material in which at least one of the above polysaccharides is bonded together and its molecular weight is increased is called cellulose or hemicellulose. The biomass may contain the above-mentioned cellulose or hemicellulose. Cellulose is composed of multiple glucans bonded together. On the other hand, hemicellulose is composed of two or more polysaccharides bonded together, and examples include glucuronoxylan, arabinoxylan, and glucomannan.

[0059] Regarding the components of acid-insoluble substances, biomass char is dissolved in 72% by mass sulfuric acid, and the residue that does not dissolve in the sulfuric acid is recovered by repeated filtration and washing. The components of the residue are then measured by pyrolysis GC-MS and evaluated based on the results. Specifically, the components of acid-insoluble substances are evaluated using the peak area of ​​the peaks detected by pyrolysis GC-MS measurement. Pyrolysis GC-MS can be performed by introducing the gas obtained by pyrolysis of the recovered residue in a helium gas atmosphere and a furnace set to 600°C into the GC-MS. The amount of detected components is slightly affected by the instrument conditions if the peak area is directly compared, so from the viewpoint of improving accuracy, it is preferable to determine the relative amount (relative concentration) based on the peak area of ​​acacia biomass molded body (acacia WP).

[0060] Therefore, the relative concentration of the components detected per unit mass of the biomass char residue B can be expressed by the following equation (3) as follows: Relative concentration = (Peak area of ​​the component detected by pyrolysis GC-MS / Mass of residue B introduced into the heating furnace) / (Peak area of ​​the component detected by pyrolysis GC-MS of acacia WP / Mass of residue A introduced into the heating furnace) (3)

[0061] The above biomass char may contain components insoluble in sulfuric acid (acid-insoluble substances), and the inclusion of such components further suppresses pulverization during manufacturing. The sulfuric acid-insoluble components may be substances that exhibit specific gas components when heated, or they may not exhibit specific gas components. Examples of such specific gas components include pentatricont-17-ene and 4-ethylphenol.

[0062] When a biomass molded body made of acacia is dissolved in 72% by mass sulfuric acid, and the residue A remaining undissolved is heated in a furnace under conditions of a helium gas atmosphere and 600°C, the amount of Pentatriacont-17-ene produced in the gas generated is defined as the amount detected per unit mass of residue A, and when the biomass char of this disclosure is dissolved in 72% by mass sulfuric acid, and the residue B remaining undissolved is heated in a furnace under conditions of a helium gas atmosphere and 600°C, the amount of Pentatriacont-17-ene detected per unit mass of residue B in the gas generated is defined as the amount detected as the amount detected as the amount of Pentatriacont-17-ene. In this case, the amount detected as B may be 0.5 times or less than the amount detected as A. That is, the relative concentration of Pentatriacont-17-ene calculated by replacing "components detected by pyrolysis GC-MS" in the above formula (3) with "Pentatriacont-17-ene detected by pyrolysis GC-MS" may be 0.5 or less. From the viewpoint of suppressing the pulverization of biomass char, the relative concentration of Pentatricont-17-ene may be 0.3 or less. Pentatricont-17-ene does not need to be present in residue B. In other words, the relative concentration of Pentatricont-17-ene may be 0.

[0063] The 2,6-Dimethoxyphenol content in the acetone extract of biomass char obtained based on ISO 14453:2014 "Pulp - Measurement of acetone-soluble substances" may be 5 mg / kg or less relative to the mass of the biomass char in its completely dry state. The 2,6-Dimethoxyphenol content may be 3 mg / kg or less. 2,6-Dimethoxyphenol may not be present in the acetone extract at all. That is, the 2,6-Dimethoxyphenol content in the acetone extract may be 0.

[0064] The 4-Ethylphenol content in the acetone extract of biomass char obtained based on ISO 14453:2014 "Pulp - Measurement of Acetone-Soluble Substances" may be 5 mg / kg or less relative to the mass of the biomass char in its dry state. The 4-Ethylphenol content may be 3 mg / kg or less. 4-Ethylphenol may not be present in the acetone extract at all. That is, the 4-Ethylphenol content in the acetone extract may be 0.

[0065] The softening point (IT), melting point (HT), and flow point (FT) of the ash contained in the biomass char may be between 1000 and 1800°C. Furthermore, when measuring the IT, HT, and FT of the ash contained in the biomass char, the temperature at which the height of the test pipe equals the width of the test pipe (ST) may also be between 1000 and 1800°C. From the viewpoint of preventing the ash from melting at low temperatures when heated and further suppressing fouling when burning solid fuel, the IT may be between 1100 and 1300°C, the HT may be between 1400 and 1600°C, the FT may be 1500°C or higher, or between 1500 and 1800°C, and the ST may be between 1300 and 1500°C.

[0066] The IT, HT, FT, and ST of ash contained in biomass char can be measured in accordance with JIS M8801:2004. Specifically, a 20-30g sample is used to create a triangular pyramid test sample with a height of 8mm, a base length of 2.7mm on two sides and 3mm on the other side, and one of the faces being 3mm long. The test is then performed by heating the pyramid in a furnace and observing its melting.

[0067] The ash composition of the biomass char may contain at least one selected from the group consisting of SiO2, Fe2O3, Al2O3, CaO, MgO, SO3, P2O5, TiO2, Na2O, K2O, V2O5, NiO2, and MnO. The content of each component in the ash composition of the biomass char can be determined by the method described in the examples.

[0068] In the ash composition of biomass char, the K2O / (Al2O3+SiO2) ratio may be 0.05-1.0, 0.2-0.8, or 0.3-0.6. In the ash composition of biomass char, the CaO / (Al2O3+SiO2) ratio may be 0.03-2.5, 0.5-2.0, or 1.0-2.0. In the ash composition of biomass char, the MgO / (Al2O3+SiO2) ratio may be 0.03-1.0, 0.1-0.7, or 0.2-0.5. By having the K2O / (Al2O3+SiO2), CaO / (Al2O3+SiO2), and MgO / (Al2O3+SiO2) ratios within the above ranges in the ash composition of biomass char, fouling of solid fuel can be suppressed.

[0069] The fuel ratio (fixed carbon / volatile matter) of biomass char may be 0.1 or higher, or 0.2 or higher, from the viewpoint of further improving combustibility. On the other hand, the fuel ratio may be 0.8 or lower, 0.5 or lower, 0.4 or lower, or 0.3 or lower. Examples of fuel ratios for biomass char may be 0.1-0.8, 0.1-0.5, 0.1-0.45, 0.1-0.4, 0.1-0.3, or 0.2-0.3. By having the fuel ratio within this range, the combustibility of the solid fuel can be further improved. The fixed carbon and volatile matter of biomass char can be measured in accordance with JIS M 8812:2006. The fixed carbon may be 10-30% by mass, 15-25% by mass, 10-25% by mass, 10-21% by mass, or 13-21% by mass. The volatile content may be 60-80% by mass, or 68-78% by mass. Having the fixed carbon of the biomass char within the above range further suppresses the pulverization of the biomass char and further improves the combustibility of the solid fuel.

[0070] The higher heating value (UH) of biomass char may be 15,000 to 25,000 kJ / kg, 19,000 to 24,000 kJ / kg, or 20,000 to 23,000 kJ / kg in a completely dry state. The UH in a completely dry state can be measured in accordance with JIS M 8814:2003. By having the UH of biomass char within the above range, the combustibility of the solid fuel can be further improved.

[0071] The moisture content of the biomass char may be 5.0% by mass or more, or 6.0% by mass or more. Alternatively, the moisture content of the biomass char may be 10.0% by mass or less, 9.0% by mass or less, or 8.0% by mass or less. An example of the range of moisture content for the biomass char may be 5.0 to 10.0% by mass, 5.0 to 9.0% by mass, or 6.0 to 8.0% by mass. Within these ranges, a solid fuel with suppressed dust generation and excellent ignition properties can be obtained.

[0072] From the viewpoint of reducing the pulverization rate of biomass char, the ash content of biomass char may be 0.1% by mass or more, 0.5% by mass or more, or 1.0% by mass or more in an oven-dry state. From the viewpoint of reducing ash in biomass char and suppressing fouling of solid fuel, the ash content of biomass char may be 5.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less in an oven-dry state. For example, the ash content of biomass char may be 0.1 to 5.0% by mass, 0.5 to 5.0% by mass, 1.0 to 5.0% by mass, 0.1 to 3.0% by mass, 0.5 to 3.0% by mass, 1.0 to 3.0% by mass, 0.1 to 2.0% by mass, 0.5 to 2.0% by mass, or 1.0 to 2.0% by mass in an oven-dry state.

[0073] The moisture content and ash content of biomass char can be measured in accordance with JIS M 8812:2006.

[0074] Biomass char may have a maximum temperature of less than 200°C or 170°C or lower in the self-heating test. The self-heating test can be performed using the wire basket test specified in the UN recommendation "Manual of Tests and Criteria 7th edition," 33.4.6 Test N.4: Test Method for self-heating Substances.

[0075] Biomass char may have a chemical oxygen demand (COD) of 1500 ppm or less, 1000 ppm or less, or 900 ppm or less. Alternatively, the COD may be 100 ppm or more, 200 ppm or more, 300 ppm or more, or 500 ppm or more. An example of the COD range is 100 to 1500 ppm or 500 to 1500 ppm. Having the COD within this range allows for a sufficient reduction in the environmental burden of wastewater generated during the production of biomass char. Here, the COD of the immersion water when biomass char is immersed in water refers to the COD value of immersion water prepared at room temperature under the following conditions, in accordance with the preparation of the immersion water sample for COD measurement, as stipulated in the method for testing metals, etc., contained in industrial waste, as specified in the Environmental Agency Notification No. 13 (i) of 1973. ·Sample:water=1:10 (mass ratio) • Shaking method: 200 times / minute in the horizontal direction • Dissolution time: 6 hours The COD value of the immersion water can be measured in accordance with JIS K 0102:2016-17 "Oxygen consumption by potassium permanganate at 100°C". The room temperature is, for example, 20°C. The room temperature may be 15-25°C or 20-25°C.

[0076] Biomass char has a bulk density of 400-700 kg / m³ according to JIS Z 8807:2012. 3 , 500~700 kg / m 3 , 550~650 kg / m 3 , or 580-650 kg / m 3 This is also acceptable. By keeping the bulk density within the above range, the pulverization rate of the biomass char can be further reduced.

[0077] The chlorine content in biomass char may be 0.001 to 0.008 mass%, or 0.002 to 0.005 mass%. The chlorine content can be measured by elemental analysis in accordance with JIS M 8813:2006.

[0078] The true specific gravity of biomass char may be 1.0–2.0 g / mL, 1.2–1.8 g / mL, or 1.4–1.7 g / mL. The true specific gravity of biomass char can be measured, for example, using an ultrapycnometer.

[0079] The BET specific surface area of ​​biomass char is 0.1 to 0.8 m². 2 / g, 0.2~0.6m 2 / g, or 0.2~0.5m 2 It may also be / g. The BET specific surface area of ​​biomass char can be measured, for example, by a constant volume method using nitrogen gas adsorption with a specific surface area / pore size analyzer.

[0080] The pore volume of the biomass char may be 0.1-0.8 mL / g, 0.2-0.6 mL / g, or 0.2-0.5 mL / g. The pore volume of the biomass char can be measured, for example, by a mercury injection method using a fully automated pore distribution analyzer.

[0081] The specific surface area of ​​biomass char is 10-40 m². 2 / g, 15-30m 2 / g, or 20-30m 2 It may also be / g. The specific surface area of ​​biomass char can be measured, for example, by a mercury injection method using a fully automated pore distribution analyzer.

[0082] The median diameter of the biomass char may be 0.5 to 5 μm, 1.0 to 4.0 μm, or 2.0 to 3.5 μm. Having a median diameter within the above range allows for sufficient mixing with pulverized coal, enabling adequate co-firing of the biomass char and pulverized coal. The median diameter of the biomass char can be measured, for example, by a mercury injection method using a fully automated pore size analyzer.

[0083] The shape of the biomass char may be cylindrical (pellet-shaped). The diameter may be 6.0 to 10.0 mm, 6.0 to 8.5 mm, or 7.0 to 8.5 mm. The length of the central axis may be 40 mm or less, or 30 mm or less. Alternatively, the length of the central axis may be 15 mm or more. Having the size of the biomass char within this range improves the manufacturing efficiency and handling of the biomass char. Note that the shape of the biomass char is not limited to cylindrical.

[0084] The volume of biomass char is 1000-2500 mm³. 3 , 1200~2000mm 3 This is also acceptable. Having the volume of biomass char within this range can improve the production efficiency and handling of the biomass char.

[0085] Biomass char does not necessarily need to be molded into a specific shape; it may be in an unformed state such as powder, chips, or flakes.

[0086] When biomass char is molded, its mechanical durability (DU) can be determined in accordance with the American agricultural industry standard ASAE S 269.4 and the German industrial standard DIN EN 15210-1. The DU value may be 90.0 or higher, or 95.0 or higher. Alternatively, the DU value may be 100 or lower. Having a DU within this range allows for sufficiently high handling properties of the biomass char. It also makes the biomass char moderately hard, further suppressing pulverization. An example of a DU range is 90.0 to 100, or 95.0 to 100.

[0087] When the biomass char is molded, the grinding work index (BMI2) of the biomass char may be 50.0 to 95.0, 65.0 to 90.0, or 70.0 to 80.0. In this disclosure, BMI2 is defined as the ratio of the mass under a 150 μm sieve to the total mass under a 1000 μm sieve of a sample that has been ground for 20 minutes according to the procedure based on JIS M 4002:2000 "Test method for grinding work index".

[0088] [Method of manufacturing solid fuel] A method for producing solid fuel according to one embodiment includes a step of mixing biomass char and pulverized coal to obtain a mixture, wherein the total amount of biomass char and pulverized coal in an oven-dry state is taken as 100% by mass, and the biomass char content is 3 to 90% by mass, and the pulverized coal content is 10 to 97% by mass. Furthermore, in the biomass char, the mannose content as constituent sugars is 2.0 to 12.0% by mass, the xylose content is 0.3 to 10.0% by mass, the arabinose content is 1.0% by mass or less, and the glucose content is 40.0 to 55.0% by mass, and the ash content of the pulverized coal is 20 to 40% by mass on an oven-dry basis. The solid fuel obtained in this way has a sufficiently reduced amount of ash that is easily melted at low temperatures, and fouling can be suppressed.

[0089] The above explanation can be applied directly to solid fuels, biomass char, and pulverized coal.

[0090] In the process of obtaining the mixture, the method of mixing the biomass char and pulverized coal is not particularly limited and can be carried out by known methods. For example, biomass char and pulverized coal measured in a predetermined mass ratio can be mixed in a mixer or the like.

[0091] The mixture may be used as a solid fuel as is. Using the mixture as a solid fuel as is can shorten the time required for solid fuel production. Alternatively, a molding process may be performed after the process of obtaining the mixture. Performing the molding process can improve the handling properties of the solid fuel.

[0092] [Method for firing solid fuels] A method for calcining a solid fuel according to one embodiment includes a step of calcining the solid fuel described above. The solid fuel described above has a sufficiently reduced amount of ash that is easily melted at low temperatures, and fouling can be suppressed.

[0093] The method for calcining the solid fuel in the calcination process is not particularly limited and can be carried out by known methods. For example, it can be calcined in coal combustion equipment such as a boiler.

[0094] This disclosure includes several embodiments described below. [1] A solid fuel comprising biomass char and pulverized coal, When the total amount of the biomass char and the pulverized coal in an oven-dried state is taken as 100% by mass, the content of the biomass char is 3 to 90% by mass, and the content of the pulverized coal is 10 to 97% by mass. In the aforementioned biomass char, the mannose content as constituent sugars is 2.0 to 12.0% by mass, the xylose content is 0.3 to 10.0% by mass, the arabinose content is 1.0% by mass or less, and the glucose content is 40.0 to 55.0% by mass. A solid fuel wherein the ash content of the pulverized coal is 20-40% by mass on an oven-dry basis. [2] The solid fuel described in [1], wherein the volatile content is 30-65% by mass, the fixed carbon is 20-68% by mass, the fuel ratio is 0.30-2.50, the higher heating value is 21,000-25,000 kJ / kg in an oven-dry state, and the ash content is 7-26% by mass on an oven-dry basis. [3] The pulverized coal has an ash softening point (IT), melting point (HT), and flow point (FT) of 1500°C or higher, as measured in accordance with JIS M8801:2004. The solid fuel according to [1] or [2], wherein when the IT, HT, and FT are measured, the temperature (ST) at which the height of the test cylinder becomes equal to the width of the test cylinder is 1500°C or higher. [4] The pulverized coal is a solid fuel according to any one of [1] to [3], wherein the ash composition has K2O / (Al2O3+SiO2) 0.05 or less, CaO / (Al2O3+SiO2) 0.05 or less, and MgO / (Al2O3+SiO2) 0.05 or less. [5] The pulverized coal has a bulk density of 500 to 1500 kg / m³ 3 A solid fuel as described in any one of [1] to [4], wherein the volatile content is 10-30% by mass, the fixed carbon is 60-80% by mass, the fuel ratio is 1.0-3.0, and the higher heating value in an oven-dry state is 20,000-30,000 kJ / kg. [6] The solid fuel according to any one of [1] to [5], wherein the content of 2,6-Dimethoxyphenol in the acetone extract according to ISO 14453:2014 in the biomass char is 5 mg / kg or less relative to the mass of the biomass char in an oven-dry state. [7] The solid fuel according to any one of [1] to [6], wherein the content of 4-Ethylphenol in the acetone extract according to ISO 14453:2014 in the biomass char is 5 mg / kg or less relative to the mass of the biomass char in an oven-dry state. [8] The biomass char is a solid fuel according to any one of [1] to [7], wherein the ash composition of the biomass char is 0.05 to 1.0 for K2O / (Al2O3+SiO2), 0.03 to 2.5 for CaO / (Al2O3+SiO2), and 0.03 to 1.0 for MgO / (Al2O3+SiO2). [9] The biomass char has a bulk density of 400-700 kg / m³ 3 A solid fuel as described in any one of [1] to [8], wherein the volatile content is 60-80% by mass, the fixed carbon is 10-30% by mass, the fuel ratio is 0.1-0.8, and the higher heating value in an oven-dry state is 15,000-25,000 kJ / kg.

[10] A biomass molded body made of acacia was dissolved in 72% by mass of sulfuric acid, and the residue A remaining undissolved was heated in a furnace under the conditions of a helium gas atmosphere and 600°C. The amount of Pentatricont-17-ene produced in the gas generated was defined as the amount detected per unit mass of residue A. When the biomass char is dissolved in 72% by mass sulfuric acid, and the undissolved residue B is heated in a furnace under a helium gas atmosphere and at 600°C, the amount of Pentatricont-17-ene detected per unit mass of residue B in the gas generated is defined as the detected amount B. The solid fuel according to any one of [1] to [9], wherein the detected amount B is 0.5 times or less than the detected amount A.

[11] A solid fuel as described in any one of [1] to

[10] , wherein when heated from room temperature at a heating rate of 20°C / min, the temperature at which the mass change after ignition is 20 μg / (min·mg) or less is 520°C or higher.

[12] A method for calcining a solid fuel, comprising the step of calcining the solid fuel described in any one of [1] to

[11] above.

[13] The process includes mixing biomass char and pulverized coal to obtain a mixture, In the above mixture, when the total amount of the biomass char and the pulverized coal in an oven-dried state is taken as 100% by mass, the content of the biomass char is 3 to 90% by mass, and the content of the pulverized coal is 10 to 97% by mass. In the aforementioned biomass char, the mannose content as constituent sugars is 2.0 to 12.0% by mass, the xylose content is 0.3 to 10.0% by mass, the arabinose content is 1.0% by mass or less, and the glucose content is 40.0 to 55.0% by mass. A method for producing a solid fuel, wherein the ash content of the pulverized coal is 20 to 40% by mass on an oven-dry basis. [Examples]

[0095] The contents of this disclosure will be explained in more detail below with reference to examples and comparative examples. However, this disclosure is not limited to the examples described below.

[0096] (Comparative Example 1) Low-grade coal powder with a high ash content was prepared. After air-drying the prepared coal powder, it was crushed using a pulverizer until the maximum particle size was 3 mm or less, thereby obtaining pulverized coal.

[0097] (Comparative Example 2) As the raw material biomass, a mixture of 30% by mass of spruce, 45% by mass of pine, and 25% by mass of fir was crushed in a pulverizer. This mixture was used as the coniferous wood hereafter. Subsequently, a molding process was carried out to form the coniferous wood that had been crushed to a particle size of 3000 μm or less. In the molding process, the crushed coniferous wood was uniaxially compressed to obtain cylindrical biomass molded bodies (hereinafter referred to as "WP") with a diameter (pellet diameter) of 8.3 mm and a length of 25 mm. Notably, the WP was obtained using only the raw coniferous wood without adding any binder. 4 kg of the obtained WP was placed into a batch-type electric small rotary kiln (manufactured by Takasago Kogyo Co., Ltd.) with a heating chamber having an inner diameter of 600 mm, and heated to 250°C at a heating rate of 2°C / min. After reaching 250°C, it was immediately air-cooled to cool the inside of the rotary kiln to room temperature to obtain biomass char. The yield was calculated from the mass of the WP and the mass of the obtained biomass char. The result showed a yield of 88.7% by mass.

[0098] [Measurement of powdering rate] The entire amount of biomass char in the rotary kiln was sieved through a 3.35 mm mesh sieve, and the pulverization rate was calculated as the mass ratio of the material below the sieve to the total mass. The sieve was used according to the procedure in accordance with JIS M 8801:2008. As a result, the pulverization rate was 5.3% by mass.

[0099] <Evaluation of physical properties> [Evaluation of self-heating properties] For Comparative Example 2, the wire basket test specified in the UN recommended test method “Manual of Tests and Criteria 7th edition,” 33.4.6 TestN.4: TestMethod for self-heating Substances, was performed, and the maximum temperature reached was measured. The results are shown in Table 1.

[0100] [Measurement of Chemical Oxygen Demand (COD)] For Comparative Example 2, the COD of the immersion water sample was measured using a method compliant with JIS K 0102:2016-17 "Oxygen consumption by potassium permanganate at 100°C". The immersion water sample for COD measurement was prepared in accordance with the method for testing metals, etc., contained in industrial waste as specified in the Environmental Agency Notification No. 13 (i) of 1973. Ten times the mass of water was added to biomass char, and the mixture was shaken horizontally at a rate of 200 times per minute for 6 hours at room temperature. The results are shown in Table 1.

[0101] [Measurement of Mechanical Durability (DU)] For Comparative Example 2, DU was measured according to the following formula (4) in accordance with the American agricultural and industrial standard ASAE S 269.4 and the German industrial standard DIN EN 15210-1. In formula (4), m0 is the mass of the sample before rotation, and m1 is the mass of the sieved sample after rotation. A sieve with a mesh size of 3.15 mm was used. The results are shown in Table 1. DU = (m1 / m0) × 100 (4)

[0102] [Measurement of true specific gravity] For Comparative Examples 1 and 2, the true specific gravity was measured using an ultrapycnometer (Ultrapyc5000, manufactured by Quantachrome.co) by the He gas displacement method. At this time, the particle size of the pulverized coal was adjusted to 3 mm or less by crushing, while the biomass char was measured in its pellet form without crushing. The results are shown in Table 1.

[0103] [Measurement of BET specific surface area] For Comparative Examples 1 and 2, the BET specific surface area was measured using a constant-volume method with nitrogen gas adsorption, employing a QUADRASORBEVO specific surface area / pore size analyzer (Quantachrome.co). The particle size of the pulverized coal was adjusted to 3 mm or less by grinding, while the biomass char was measured in pellet form without grinding. The results are shown in Table 1.

[0104] [Measurement of pore volume, specific surface area, and median diameter] For Comparative Examples 1 and 2, the pore volume was determined as the cumulative volume of pores in the sample using the mercury injection method with a fully automated pore distribution analyzer (PoreMaster60-GT, manufactured by QuantaChrome Co.). The specific surface area and median diameter were also determined using the mercury injection method. The results are shown in Table 1.

[0105] [Measurement of bulk density] The bulk density of Comparative Example 1 and Comparative Example 2 was determined based on JIS Z 8807:2012. The results are shown in Table 1.

[0106] [Measurement of industrial analysis values] For Comparative Examples 1 and 2, moisture content, ash content, fixed carbon, and volatile matter were determined in accordance with JIS M 8812:2006. The fuel ratio (fixed carbon / volatile matter) was calculated from the determined fixed carbon and volatile matter. The results are shown in Table 1. In Table 1, values ​​with (-ad) indicate measurement results under normal atmospheric conditions, and values ​​with (-dry) indicate measurement results under completely dry conditions.

[0107] [Measurement of higher heating value] The higher heating value (HQ) was measured for Comparative Example 1 and Comparative Example 2 in accordance with JIS M 8814:2003. The results are shown in Table 1. The HQ was determined under both normal atmospheric conditions and in an oven-dry state.

[0108] [Measurement of grinding work index (BMI2)] The biomass char in Comparative Example 2 was pulverized using a ball mill for 20 minutes. The ball mill conforming to JIS M 4002:2000 was used, and a cylindrical container with an inner diameter of 305 mm and an axial length of 305 mm was filled with standard grade ball bearings specified in JIS B 1501:2009 (43 bearings with a diameter of 36.5 mm, 67 bearings with a diameter of 30.2 mm, 10 bearings with a diameter of 24.4 mm, 71 bearings with a diameter of 19.1 mm, and 94 bearings with a diameter of 15.9 mm), and rotated at a speed of 70 rpm. After pulverization, the material was sieved using a sieve with a mesh size of 1000 μm, and the material below the sieve was further sieved using a sieve with a mesh size of 150 μm. The ratio of the mass below the sieve with a mesh size of 150 μm to the mass below the sieve with a mesh size of 1000 μm was calculated, and this value was defined as BMI2. The results are shown in Table 1.

[0109] [Measurement of chlorine content] For Comparative Example 1 and Comparative Example 2, the chlorine content was measured in accordance with JIS M 8813. The results are shown in Table 1.

[0110] [Measurement of ash composition] In Comparative Example 1, pulverized coal was ground to a particle size of 212 μm or less in an air-dried state in accordance with JIS M 8811:2000 to obtain a sample. An air-dried state is defined as a state where the moisture content is in equilibrium with the humidity of the air. The obtained sample was heated to 815°C for 1 hour in accordance with JIS M8812:2006 to ash it, and used as the measurement sample. For sulfur content, the measurement sample was quantified using a sulfur analyzer (S832, LECO) in accordance with JIS M8819:1997, and the sulfur content was calculated as SO3. For components other than sulfur, the measurement sample was further heated to 815°C for 1 hour, and then quantified using the fundamental parameter method with an X-ray fluorescence spectrometer (ZSX Primus II, Rigaku), and the oxide content was calculated. The results are shown in Table 1.

[0111] For Comparative Example 2, the ash composition of the biomass char was determined in accordance with ISO 18122:2022 "Solid biofuels - Determination of ash content." The biomass char was heated to 550°C for 2 hours to produce a ash sample, which was then used for measurement. The ash composition of the measurement sample was quantified using the fundamental parameter method with an X-ray fluorescence spectrometer (JSX-1000S, JEOL Ltd.) and calculated as the oxide content. The results are shown in Table 1. Note that the ash composition in Table 1 indicates the content of each component in the ash.

[0112] The Na+K content was calculated by substituting the Na2O and K2O content, moisture content, and ash content measured in Comparative Example 1 into the following equation (2). The results are shown in Table 1. Note that the moisture content and ash content in the following equation (2) are measured under normal conditions. Na+K=(Na2O×46 / 62+K2O×78 / 96)×(ash content) / (1-moisture content / 100)×100 (2)

[0113] [Measurement of ash melting point] IT, HT, FT, and ST of Comparative Example 1 were measured in accordance with JIS M8801:2004. The results are shown in Table 1.

[0114] <Component analysis of biomass char> To measure the content of constituent sugars in the biomass char of Comparative Example 2, the biomass char was decomposed with acid and the constituent sugars were analyzed by GC-MS. Acid-insoluble components were measured by thermal decomposition GC-MS analysis, in which the residue was heated and decomposed. In the thermal decomposition GC-MS analysis, the thermal decomposition temperature was set to 600°C to detect acid-insoluble organic components. In addition, to investigate the resin components that bind the char aggregates together in the biomass char, an acetone extract of the biomass char was analyzed by GC-MS. Details of each analysis method are described below.

[0115] [Measurement of the content of constituent sugars] For Comparative Example 2, the content of arabinose, xylose, mannose, glucose, and galactose as constituent sugars of the polysaccharide was measured according to the method of the National Renewable Energy Laboratory (NREL) in the United States (http: / / www.nrel.gov / docs / gen / fy13 / 42618.pdf) as described in Non-Patent Document 2. Specifically, 3 mL of 72% by mass sulfuric acid was added to 0.3 g of the sample, reacted at 30°C for 1 hour, then diluted the sulfuric acid concentration to 4% by mass with water, and autoclaved at 121°C for 1 hour using a glass pressure vessel. After adding ribose as an internal standard to the vessel, the acid-insoluble lignin was filtered. After derivatization of the filtrate using the aldonitrile-acetylation method, the content of glucose, xylose, arabinose, galactose, and mannose in the filtrate was measured using GC-MS. While NREL uses HPLC for analysis, Non-Patent Document 2 uses GC-MS, which is more versatile and has better selectivity, and we also used GC-MS in this study. Therefore, the measurements were performed after derivatizing the filtrate using the aldonitrile acetylation method.

[0116] To correct for monosaccharide over-decomposition, standard solutions of known concentrations were prepared, sulfuric acid was added to achieve a total concentration of 4% by mass, and then the solutions were autoclaved at 121°C for 1 hour. The recovery rate of the standard solutions prepared in this way was used as the polysaccharide conversion factor. The polysaccharide conversion factors were 0.88 for arabinose, 0.88 for xylose, 0.90 for mannose, 0.90 for glucose, and 0.90 for galactose. The content of arabinan, xylan, mannan, glucan, and galactan was determined by multiplying the content of constituent sugars in the obtained biomass char by the polysaccharide conversion factor. The results are shown in Table 2.

[0117] [Measurement of acid-insoluble substances] For the biomass char of Comparative Example 2, the acid-insoluble matter was measured. Using the same method as described above for [measurement of constituent sugar content], 3 mL of 72% by mass sulfuric acid was added to 0.3 g of the sample, and after reacting at 30°C for 1 hour, the sulfuric acid concentration was diluted with water to 4% by mass. Then, the sample was autoclaved at 121°C for 1 hour using a glass pressure vessel, and subsequently filtered using a suction filtration bottle and washed repeatedly with water and boiling water to remove the sulfuric acid and collect the residue.

[0118] The recovered residue was introduced into a heating furnace set to 600°C under a helium atmosphere. The generated gas was directly subjected to pyrolysis GC-MS analysis using a GC-MS, and the relative concentration was calculated. The conditions for the heating furnace and GC-MS equipment were as follows.

[0119] [Heating furnace] Equipment: Frontier Labs "EGA / PY-3030D" Heating conditions: Instantaneous heating at 600°C Atmosphere: He

[0120] [GC-MS] Equipment: Shimadzu Corporation "QP-2010Ultra" Column: Restek "Rtx5 Amine" Inner diameter: 0.25 mm, Length: 30 m, Film thickness: 0.5 μm Column temperature: 40°C - 10°C / min heating - 280°C (hold) Inlet temperature: 280℃ Interface temperature: 300℃ Carrier gas: He, Carrier gas flow rate: 1.8 mL / min Ionization method: Electron ionization (EI) Measurement mass range (m / z): 10~600

[0121] Relative concentration is a value that can be calculated using the following formula (5). Relative concentration = (Peak area detected by pyrolysis GC-MS of each component / Mass of sample placed in the heating furnace) ÷ (Peak area of ​​each component detected by pyrolysis GC-MS of acacia WP / Mass of sample placed in the heating furnace) (5)

[0122] The peak area was calculated by defining the baseline as the peak start position (where the peak rises) and the base end position (where the peak ends). The baseline was defined by connecting these two points, and the area enclosed by the curve passing through this baseline and the peak top was defined as the peak area.

[0123] Table 2 shows the results of measuring the relative concentrations of heptacosan-1-ol and pentatricont-17-ene per sample mass. The relative concentration of heptacosan-1-ol was determined using pentatricont-17-ene from acacia WP as the reference.

[0124] [GC-MS and pyrolysis compounds of acetone extract] For the biomass char of Comparative Example 2, approximately 10 g of freeze-pulverized sample was used to calculate the acetone extract component in accordance with "ISO 14453: Pulpes - Determination of acetone-soluble matter". Qualitative analysis of the acetone extract component was performed by diluting a portion of the extract with acetone and then analyzing it using a gas chromatograph-mass spectrometer (GC-MS). As a result, no peaks indicating catechol, 4-ethylphenol, or 2,6-dimethoxyphenol were detected.

[0125] A portion of the diluted acetone extract was derivatized with trimethylsilyl (TMS) by adding a BSTFA derivatization reagent, and then analyzed by GC-MS to identify and perform a simplified quantitative analysis of the major derivatized components. The simplified quantitative analysis was expressed as a converted concentration relative to vanillin, using vanillin present in all samples as the reference. Specifically, a calibration curve was obtained from the vanillin standard solution and expressed by the following equation (6). Vanillin equivalent concentration (mg / kg) = (Peak area of ​​each component / Peak area of ​​vanillin standard solution) × Vanillin standard solution concentration × Acetone extract volume × Dilution ratio / Mass of biomass char in a completely dry state (6)

[0126] Table 2 shows the measured acetone extract (mass%), and the vanillin-equivalent concentrations of catechol, 4-ethylphenol, and 2,6-dimethoxyphenol.

[0127] The instrumental analysis conditions are as follows: Equipment: [GC] Nexis GC-2030 (manufactured by Shimadzu Corporation) [MS] GCMS-TQ8040NX (manufactured by Shimadzu Corporation) Column: HP-5MS (Agilent Technologies, inner diameter: 0.25 mm, length: 30 m, film thickness: 0.25 μm) Column temperature: 80°C (hold for 1 min) - 5°C / min heating - 300°C (hold for 25 min) Inlet temperature: 250°C, Transfer line temperature: 300°C Carrier gas: He 1.2 mL / min (constant flow rate) Injection method: Split (10:1) Injection volume: 1μL Ionization method: Electron ionization (EI) Measurement method: SCAN (m / z:20~500)

[0128] [Production of solid fuels] (Example 1) The pulverized coal from Comparative Example 1 and the biomass char from Comparative Example 2 were weighed and mixed in a completely dry state in a mass ratio of pulverized coal:biomass char = 75:25 to obtain a solid fuel.

[0129] (Example 2) A solid fuel was obtained using the same procedure as in Example 1, except that the pulverized coal and biomass char were mixed in a mass ratio of 50:50.

[0130] (Example 3) Solid fuel was obtained using the same procedure as in Example 1, except that the pulverized coal and biomass char were mixed in a mass ratio of 25:75.

[0131] [Calculation of each physical property value in Examples 1-3] For the solid fuels of Examples 1 to 3 shown in Tables 1 and 2, the measurement results for industrial analysis values, higher heating value, ash composition, constituent sugars, thermal decomposition GC-MS of acid-insoluble substances, and GC-MS of acetone extracts were calculated by weight-averaging the measurement results of Comparative Examples 1 and 2 based on the following formula (7). The calculation results are shown in Tables 1 and 2. (Physical properties of solid fuel) = (Measured value for pulverized coal) × (1 - Biomass char content / 100) + (Measured value for biomass char) × (Biomass char content) / 100 (7)

[0132] For the ash composition of the solid fuels in Examples 1 to 3, the biomass char content on a mass basis of the ash in the solid fuel was first calculated on an oven-dry basis using the following formula (8). The obtained (biomass char content on a mass basis of ash) was used as (biomass char content) in the above formula (7), and the measured results of the ash composition of Comparative Examples 1 and 2 were weighted averaged to calculate the biomass char content. The results are shown in Table 1. (Biomass char content on a mass basis of ash) = (Biomass char content) × (Amount of ash in a completely dry state of biomass char) / [(Biomass char content) × (Amount of ash in a completely dry state of biomass char) + (100 - Biomass char content) × (Amount of ash in a completely dry state of pulverized coal)] × 100 (8)

[0133] In each example and comparative example, the K2O / (Al2O3+SiO2), CaO / (Al2O3+SiO2), and MgO / (Al2O3+SiO2) ratios were calculated from the ash composition. The results are shown in Table 2.

[0134] In Examples 1 to 4, bulk density was measured according to JIS Z 8807:2012. The results are shown in Table 1.

[0135] [Calculation of fouling occurrence rate] The degree of fouling occurrence was calculated using the thermodynamic calculation software "FactSage Ver. 8.1" as an indicator. The simulated temperature range was from 500°C to 1700°C. The simulation atmosphere conditions were O2 concentration at 21 vol%, CO2 concentration at 0.1 vol%, and pressure at 1 atm. The ash composition was the same as that of Examples 1-3 and Comparative Examples 1 and 2, as shown in Table 1. Under these conditions, simulations were performed to determine the proportions of chemical species, solid solutions, and melts that exist stably in chemical equilibrium. The criterion for fouling was the melt proportion at 1100°C, and this melt proportion was calculated for each example and comparative example. The results are shown in Table 2. A graph showing the relationship between temperature and melt proportion is shown in Figure 1.

[0136] [Evaluation of flammability] Ignition and combustion sustainability were determined for each of the solid fuels of Examples 1-3, the pulverized coal of Comparative Example 1, and the biomass char of Comparative Example 2, using TG-DTA (STA7300, Hitachi High-Tech Science Co., Ltd.). The measurement conditions involved adding approximately 10 mg of the sample, which had been finely ground to a maximum particle size of 212 μm or less, and heating it at 20°C / min while flowing nitrogen gas containing 21 volume% O2 as a carrier gas. A graph showing the relationship between temperature and mass (TG curve) is shown in Figure 2. A graph showing the relationship between temperature and mass change (DTG curve) is shown in Figure 3.

[0137] In Figure 3, a peak was observed in the 350°C to 380°C range due to mass loss originating from volatile components of biomass. The temperature at which the peak was observed was determined as the ignition temperature. The maximum value of the peak was also determined. Furthermore, as an evaluation of combustion sustainability, the burn-out temperature at which the mass change was first 20 μg / (min·mg) or less after ignition was determined. The results are shown in Table 2.

[0138] [Calculation of CO2 reduction rate] The following formula (9) was used to calculate the solid fuels of Examples 1-3, the pulverized coal of Comparative Example 1, and the biomass char of Comparative Example 2. The results are shown in Table 2. [CO2 reduction rate (%)] = [1 - (Pulverized coal content × Higher heating value of pulverized coal in an oven-dry state) / (Pulverized coal content × Lower heating value of pulverized coal (considering moisture content) + Biomass char content × Lower heating value of biomass char (considering moisture content))] × 100 (9) In equation (9), the moisture content of the pulverized coal was 10.5% by mass, and the moisture content of the biomass char, i.e., the moisture content of the coniferous tree char, was 20.0% by mass.

[0139] Tables 1 and 2 are shown below. In Tables 1 and 2, items that were not measured are indicated with "-". In Table 2, "0" for constituent sugars indicates that the value is below the detection limit. In Tables 1 and 2, all physical properties for Comparative Example 1 and Comparative Example 2 are measured values. In Examples 1 to 4, the physical properties in Table 1 are calculated values ​​obtained by formula (7) or formula (8). Also, in Examples 1 to 4, among the physical properties in Table 2, the relative concentrations of constituent sugars, Pentatricont-17-ene and Heptacosan-1-ol, acetone extract (mass%), Catechol, 4-Ethylphenol, and 2,6-Dimethoxyphenol are calculated values ​​obtained by formula (7), while the other values ​​are measured values.

[0140] [Table 1]

[0141] [Table 2]

[0142] As shown in Table 2, the index indicating the degree of fouling was 8 for Comparative Example 1, compared to 40 for Comparative Example 2. Therefore, it was shown that when 100% biomass char is used, the ash melts easily and fouling is likely to occur. In Examples 1 to 3, where biomass char was mixed with pulverized coal, the degree of fouling was lower than in Comparative Example 2, demonstrating that fouling can be suppressed by mixing pulverized coal with biomass char.

[0143] In the ash composition, it was confirmed that as the values ​​of K2O / (Al2O3+SiO2), CaO / (Al2O3+SiO2), and MgO / (Al2O3+SiO2) decreased, the degree of fouling also decreased, indicating that fouling could be further suppressed. Therefore, it is thought that fouling can be further suppressed by reducing the proportion of low-melting-point ash.

[0144] Furthermore, as shown in Table 2 and Figure 3, it was confirmed that the solid fuels of Examples 1-3 ignited at around 360°C due to the biomass char. It was also confirmed that the burn-out temperature after ignition increased as the amount of pulverized coal increased. Therefore, it was demonstrated that solid fuels mixed with pulverized coal and biomass char can maintain both ignition and combustion sustainability. In addition, it was shown that mixing biomass char with pulverized coal can increase the CO2 reduction rate. [Industrial applicability]

[0145] According to this disclosure, it is possible to provide a solid fuel that contains biomass but can suppress fouling, a method for calcining the solid fuel, and a method for producing the solid fuel.

Claims

1. A solid fuel containing biomass char and pulverized coal, When the total amount of the biomass char and the pulverized coal in an oven-dried state is taken as 100% by mass, the content of the biomass char is 3 to 90% by mass, and the content of the pulverized coal is 10 to 97% by mass. In the aforementioned biomass char, the mannose content as constituent sugars is 2.0 to 12.0% by mass, the xylose content is 0.3 to 10.0% by mass, the arabinose content is 1.0% by mass or less, and the glucose content is 40.0 to 55.0% by mass. A solid fuel wherein the ash content of the pulverized coal is 20 to 40% by mass on an oven-dry basis.

2. The solid fuel according to claim 1, wherein the volatile content is 30 to 65% by mass, the fixed carbon content is 20 to 68% by mass, the fuel ratio is 0.30 to 2.50, the higher heating value is 21,000 to 25,000 kJ / kg in an oven-dry state, and the ash content is 7 to 26% by mass on an oven-dry basis.

3. The aforementioned pulverized coal has an ash softening point (IT), melting point (HT), and flow point (FT) of 1500°C or higher, as measured in accordance with JIS M8801:2004. The solid fuel according to claim 1 or 2, wherein when the IT, HT, and FT are measured, the temperature (ST) at which the height of the test cylinder becomes equal to the width of the test cylinder is 1500°C or higher.

4. The fine pulverized coal has, in its ash composition, K ２ O / (Al ２ O ３ +SiO ２ ) of 0.05 or less, CaO / (Al ２ O ３ +SiO ２ ) of 0.05 or less, and MgO / (Al ２ O ３ +SiO ２ ) of 0.05 or less. The solid fuel according to claim 1 or 2.

5. The aforementioned pulverized coal has a bulk density of 500 to 1500 kg / m³. ３ The solid fuel according to claim 1 or 2, wherein the volatile content is 10 to 30% by mass, the fixed carbon content is 60 to 80% by mass, the fuel ratio is 1.0 to 3.0, and the higher heating value in an oven-dry state is 20,000 to 30,000 kJ / kg.

6. The solid fuel according to claim 1 or 2, wherein the content of 2,6-Dimethoxyphenol in the acetone extract according to ISO 14453:2014 in the biomass char is 5 mg / kg or less relative to the mass of the biomass char in an oven-dry state.

7. The solid fuel according to claim 1 or 2, wherein the content of 4-Ethylphenol in the acetone extract according to ISO 14453:2014 in the biomass char is 5 mg / kg or less relative to the mass of the biomass char in an oven-dry state.

8. The aforementioned biomass charred material has an ash composition in which K ２ O / (Al ２ O ３ +SiO ２ ) is 0.05 to 1.0, CaO / (Al ２ O ３ +SiO ２ ) is 0.03 to 2.5, and MgO / (Al ２ O ３ +SiO ２ The solid fuel according to claim 1 or 2, wherein the ratio is 0.03 to 1.

0.

9. The aforementioned biomass char has a bulk density of 400 to 700 kg / m³. ３ The solid fuel according to claim 1 or 2, wherein the volatile content is 60 to 80% by mass, the fixed carbon content is 10 to 30% by mass, the fuel ratio is 0.1 to 0.8, and the higher heating value in an oven-dry state is 15,000 to 25,000 kJ / kg.

10. A biomass molded body made of acacia was dissolved in 72% by mass sulfuric acid, and the residue A remaining undissolved was heated in a furnace under helium gas atmosphere and 600°C. The amount of Pentatricont-17-ene produced in the gas generated was defined as the amount detected per unit mass of residue A. When the biomass char is dissolved in 72% by mass sulfuric acid, and the undissolved residue B is heated in a furnace under helium gas atmosphere and 600°C, the amount of Pentatricont-17-ene detected per unit mass of residue B in the gas generated is defined as the detected amount B. The solid fuel according to claim 1 or 2, wherein the detected amount B is 0.5 times or less of the detected amount A.

11. The solid fuel according to claim 1 or 2, wherein when heated from room temperature at a heating rate of 20°C / min, the temperature at which the mass change after ignition becomes 20 μg / (min·mg) or less is 520°C or higher.

12. A method for firing a solid fuel, comprising the step of firing the solid fuel according to claim 1 or 2.

13. The process includes a step of mixing biomass char and pulverized coal to obtain a mixture. In the above mixture, when the total amount of the biomass char and the pulverized coal in an oven-dried state is taken as 100% by mass, the content of the biomass char is 3 to 90% by mass, and the content of the pulverized coal is 10 to 97% by mass. In the aforementioned biomass char, the mannose content as constituent sugars is 2.0 to 12.0% by mass, the xylose content is 0.3 to 10.0% by mass, the arabinose content is 1.0% by mass or less, and the glucose content is 40.0 to 55.0% by mass. A method for producing a solid fuel, wherein the ash content of the pulverized coal is 20 to 40% by mass on an oven-dry basis.

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