JP6910546B2 - Molded fuel and its manufacturing method - Google Patents

Description

The present disclosure relates to a molded fuel and a method for producing the same.

In recent years, the price of steam coal, which is coal used for coal-fired power generation, has risen due to an increase in power generation demand mainly in emerging countries, and stable supply remains uncertain. Therefore, a technique for using low-grade coal such as lignite and subbituminous coal, which are inexpensive and have a large recoverable reserve, as a substitute for steam coal for coal-fired power generation is being studied (see, for example, Patent Document 1).

Since coal-fired power generation _{emits a large amount of CO 2 , as a means of reducing CO 2} in coal-fired power generation as a measure against global warming, a technology for co-firing biomass, which is a renewable energy, when burning coal is used. It is being considered. Since biomass has poor pulverizability and tends to have a small calorific value, when woody biomass is used as it is for co-firing, the co-firing rate is only about 3% in terms of calorific value.

Therefore, Patent Document 2 proposes a technique for roasting biomass in order to improve pulverizability. Further, Patent Document 3 proposes a technique for roasting biomass in order to improve the calorific value of biomass. In these Patent Documents 2 and 3, it is proposed to use the solid fuel obtained by roasting biomass by co-firing with coal.

The solid fuel may be stored in a silo or the like, for example. As an index of the safety of solid fuel, the R70 method for evaluating the spontaneous combustion property of coal is known (see Patent Document 4 and Non-Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-23280 International Publication No. 2014/050964 JP-A-2017-39933 Japanese Unexamined Patent Publication No. 2019-066296

B. Beamish et al. Adiabatic testing procedures for determining the self-heating propensity of coal and sample aging effects, Thermochimica Acta 362 (2000) 79-87

When low-grade coal such as lignite and subbituminous coal is used as a substitute for steam coal for coal-fired power generation, the calorific value of the low-grade coal is small, so it is necessary to improve the calorific value of the alternative fuel to the calorific value equivalent to steam coal. There is. In addition, _{when biomass is co-fired to reduce CO 2} , it is necessary to pulverize the biomass before supplying it to the combustion equipment, so it is necessary to make the biomass easily crushed. Moreover, since the calorific value of biomass is smaller than that of coal, a technique for improving the calorific value to the equivalent of steam coal is required.

When coal and solid fuel obtained from biomass are used by co-firing in a combustion facility such as a boiler, it is necessary to handle the coal and solid fuel obtained from biomass separately until they are supplied to the combustion facility. In addition, if coal and solid fuel obtained from biomass are mixed before being supplied to the combustion equipment, the bulk densities of the two will differ, resulting in a large variation in the mixing ratio and fluctuations in the amount of heat supplied, resulting in operation of the combustion equipment. Is concerned about instability.

Therefore, the present disclosure provides a method for producing a molded fuel capable of producing a molded fuel having a high calorific value and excellent handleability while using biomass having a bulk density different from that of coal. Further, it provides a molded fuel having a high calorific value and excellent handleability while containing biomass having a bulk density different from that of coal.

The method for producing a molded fuel according to one aspect of the present disclosure includes a carbonization step of carbonizing coal containing at least one of brown coal and sub-bituminous coal to obtain dry distillation coal, and a biomass semi-carbonized product obtained by semi-carbonizing dry distillation coal and biomass. It has a molding step of molding a mixture containing and to obtain a molding fuel.

In the above-mentioned production method, since dry distillation coal having a high carbon component ratio and a high calorific value is used by the carbonization step, it is possible to increase the calorific value as compared with the case of using coal containing at least one of lignite and subbituminous coal. can. Further, since it is used as a molding fuel by a molding process, it is superior in handleability as compared with a fuel in which both are simply mixed without molding. Therefore, it is possible to produce a molded fuel having a high calorific value and excellent handling while using biomass. Further, the molded fuel has a small fuel ratio (fuel ratio = fixed carbon (FC) / volatile content (VM)) because it contains biomass semi-carbide. When the fuel ratio is small, the volatile content is high, so that the ignitability is high, and the volatile content is removed immediately after the start of combustion, so that the molded fuel becomes porous and the specific surface area becomes large. This makes it easier to burn and has excellent combustibility.

The above-mentioned production method includes a semi-carbonization step of semi-carbonizing biomass to obtain a biomass semi-carbide and a crushing step of crushing the biomass semi-carbide, and the crushed biomass semi-carbide and dry distillation coal are mixed and mixed. May be obtained. Biomass semi-carbide is easier to grind than biomass. Therefore, the time and energy required for pulverization can be reduced. Therefore, the molded fuel can be efficiently produced.

The above-mentioned production method may have an oxidation treatment step of oxidizing the dry distillation coal and the biomass semi-carbide, respectively. Further, in the oxidation treatment step, the dry distillation coal may be heated to a temperature range of 160 ° C. or higher and 240 ° C. or lower, and the biomass semi-carbide may be heated to a temperature range of 100 ° C. or higher and lower than 200 ° C. As a result, the surface components of the carbonization coal and the biomass semi-carbide are oxidized to stabilize the surface state, so that the self-heating property is reduced and the pyrophoricity is suppressed. In addition, oxidative decomposition associated with the oxidation treatment is suppressed, and the yield of the molded fuel can be increased.

The above-mentioned production method may include a semi-carbonization step of semi-carbonizing biomass using the sensible heat of carbonization to obtain a mixture. In this production method, since the biomass is semi-carbonized using the actual heat of the carbonization coal, it is possible to efficiently produce the biomass semi-carbide and the molded fuel with less energy loss.

The above-mentioned production method may include a pulverization step of pulverizing the mixture before the molding step. Biomass semi-carbide is easier to grind than biomass. Therefore, the time and energy required for pulverization can be reduced. Therefore, the molded fuel can be produced more efficiently. The grinding step may be between the semi-carbonization step and the molding step.

In the above-mentioned production method, biomass may be heated to 200 to 450 ° C. and semi-carbonized by mixing it with dry distillation coal in a temperature range of 400 to 800 ° C. Thereby, a biomass semi-carbide having a high calorific value and good pulverizability can be produced sufficiently efficiently. The temperature of the biomass mixed with the carbonization coal may be 150 ° C. or lower.

The above-mentioned production method may include an oxidation treatment step of oxidizing the mixture in a temperature range of 140 ° C. or higher and 240 ° C. or lower. As a result, the surface components of the carbonization coal and the biomass semi-carbide are oxidized to stabilize the surface state, so that the self-heating property is reduced and the pyrophoricity is suppressed. In addition, oxidative decomposition associated with the oxidation treatment is suppressed, and the yield of the molded fuel can be increased.

Before semi-carbonizing the biomass, it has a coarse pulverization step of coarsely pulverizing the biomass so that the average value of the particle size of the biomass exceeds 7 mm and less than 50 mm, and a drying step of drying the coarsely pulverized biomass. You may. As a result, the handleability can be further improved while sufficiently advancing the semi-carbonization of the biomass.

In the molding step, the mixture may be molded using a binder containing polyvinyl alcohol having a saponification degree of 99 mol% or more. By using polyvinyl alcohol having a high degree of saponification, the water resistance of the molded fuel can be improved. Further, when polyvinyl alcohol having a high degree of saponification is dried, the hydroxyl groups in each molecule are bonded to each other by hydrogen bonds, and exhibit excellent water resistance. That is, the molecules of polyvinyl alcohol contained as a binder in the molded fuel are firmly bonded to each other, so that high strength can be maintained even when wet with water.

The degree of polymerization of the polyvinyl alcohol is preferably 1700 or more. This makes it possible to further improve the strength of the molded fuel, especially during drying.

The molded fuel obtained by the above-mentioned production method preferably has a COD of 500 mass ppm or less when immersed in water 13 times its mass at 25 ° C. for 2 days. As a result, the impact on the environment can be sufficiently reduced even if the products are piled up in the yard, for example.

The molded fuel according to one aspect of the present disclosure includes dry distillation coal and biomass semi-carbide of coal containing at least one of lignite and subbituminous coal. Since this molded fuel contains dry distillation coal, it is possible to achieve a higher calorific value than when it contains coal. Further, since it is a molded fuel containing carbonization coal and biomass semi-carbide, it is excellent in handleability as compared with a fuel in which both are simply mixed without molding. Further, the molded fuel has a small fuel ratio (fuel ratio = fixed carbon (FC) / volatile content (VM)) because it contains biomass semi-carbide. When the fuel ratio is small, the volatile content is high, so that the ignitability is high, and the volatile content is removed immediately after the start of combustion, so that the molded fuel becomes porous and the specific surface area becomes large. This makes it easier to burn and has excellent combustibility.

The molding fuel may contain polyvinyl alcohol having a saponification degree of 99 mol% or more. As a result, the crushing strength of the molded fuel can be sufficiently increased, and the water resistance can also be improved.

When the molding fuel is immersed in 13 times the mass of water at 25 ° C. for 2 days, the COD of the water is preferably 500 mass ppm or less. As a result, the impact on the environment can be sufficiently reduced even if the products are piled up in the yard, for example.

According to the present disclosure, it is possible to provide a method for producing a molded fuel capable of producing a molded fuel having a high calorific value and excellent handleability while using biomass having a bulk density different from that of coal. Further, it is possible to provide a molded fuel having a high calorific value and excellent handleability while containing biomass having a bulk density different from that of coal.

FIG. 1 is a flowchart of a molding fuel manufacturing method according to an embodiment. FIG. 2 is a schematic view of an apparatus for measuring the strength of molded fuel. FIG. 3 is a flowchart of a molding fuel manufacturing method according to another embodiment. FIG. 4 is a graph showing the relationship between the semi-carbonized temperature of biomass and the calorific value of the semi-carbonized biomass. FIG. 5 is a graph showing the evaluation results of the Hardgrove Grindability Index (HGI) of biomass semi-carbide. FIG. 6 is a graph showing a change in crushing strength depending on the amount of polyvinyl alcohol added. FIG. 7 is a graph showing the measurement results of the calorific value of oxidation of the mixture and coal. FIG. 8 is a graph showing the measurement results of calorific value of oxidation of dry distillation coal, biomass semi-carbide and coal. FIG. 9 is a diagram showing a two-stage combustion type test apparatus used in the experimental example. FIG. 10 is a graph showing the relationship between the unburned content and the NOx concentration when the solid fuel of Examples 2 to 5 and the bituminous coal of Reference Example 2 are burned. FIG. 11 is a graph showing the evaluation results of the self-heating properties of the solid fuels of Examples 2 to 5 and the bituminous coal of Reference Example 2 by the R70 method.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings as the case may be. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.

[Molded fuel and its manufacturing method]
FIG. 1 is a flowchart of a molding fuel manufacturing method according to the present embodiment. The method for producing the molding fuel of the present embodiment includes a coarse crushing step S1 for coarsely crushing the biomass, a drying step S2 for drying the biomass, a crushing step S3 for crushing coal containing at least one of brown coal and subbituminous coal, and crushing. The drying step S4 for drying the coal, the dry distillation step S5 for obtaining dry distillation coal by carbonizing the dried coal, and the dry distillation coal and the biomass are mixed, and the biomass is semi-carbonized using the actual heat of the dry distillation coal to obtain the biomass. It has a semi-carbonization step S6 for obtaining a mixture of semi-carbonized material and carbonized coal, a crushing step S7 for crushing the mixture, and a molding step S8 for molding the pulverized product to obtain molding fuel.

In this embodiment, as a raw material, coal containing at least one of biomass, lignite and subbituminous coal is used. Biomass refers to biological resources other than fossil fuels. Examples of biomass include thinned wood, pruned branches, waste wood, bark chips, other wood, bamboo, grass, coconut husks, palm oil residue, vegetables, fruits, food residue, sludge and the like. Among these biomasses, woody biomass such as thinned wood, pruned branches, waste wood, bark chips, and other wood is preferable. The coal may be low-grade coal such as subbituminous coal and lignite from the viewpoint of effective use of resources. Even when low-grade coal is used, pyrophoricity can be suppressed by reducing the surface area as a molding fuel.

In the coarse crushing step S1, the biomass is cut and crushed. The size of the crushing is not particularly limited, but from the viewpoint of improving the handleability in the subsequent process, the average value of the particle size is preferably more than 7 mm, more preferably 10 mm or more. On the other hand, from the viewpoint of sufficiently advancing the semi-carbonization in the semi-carbonization step described later, the average value of the particle size is preferably less than 50 mm, more preferably less than 40 mm. The average value of the particle size is the particle size at which the cumulative weight ratio when the crushed biomass pieces are sieved and the particle size is distributed is 50%. The bulk density of the biomass may be, for example, 0.1 to 0.6 g / cm ^3. The water content of the biomass may be, for example, 10 to 60% by mass, or 30 to 60% by mass.

In the drying step S2, the biomass is dried in the air, for example, in a temperature range of 20 to 150 ° C. The drying step S2 may be performed in an atmosphere of an inert gas. Further, it may be carried out in the exhaust gas of the combustion furnace. In the drying step S2, the water content of the biomass is reduced to, for example, 0 to 30% by mass. By performing the drying step, the semi-carbonization of biomass in the semi-carbonization step described later can proceed smoothly.

The drying step S2 may be performed using an ordinary electric furnace or the like, or may be performed using an indirect heater or an air fluidized bed dryer. The time of the drying step S2 is not particularly limited and can be adjusted according to the water content and size of the biomass.

In the crushing step S3, coal is crushed. The size of the crushing is also not particularly limited, but from the viewpoint of smooth carbonization, the average particle size of the coal is preferably less than 50 mm, more preferably less than 30 mm, and further preferably less than 10 mm. The average value of the particle size is the particle size at which the cumulative weight ratio when the crushed coal fragments are sieved and the particle size is distributed is 50%. The water content of coal is, for example, 30 to 60% by mass. The next drying step S4 is performed according to the water content of the coal.

In the drying step S4, the coal is dried by heating it in the air, for example, in a temperature range of 40 to 150 ° C. The drying step S4 may be performed in an atmosphere of an inert gas. Further, it may be carried out in the exhaust gas of the combustion furnace. In the drying step S4, the water content of coal is reduced to, for example, 10 to 20% by mass. By performing such a drying step S4, the heat load in the carbonization step can be reduced, the carbonization equipment can be miniaturized, and the equipment cost can be reduced.

The drying step S4 may be performed using an ordinary electric furnace or the like, or may be performed using an indirect heater or an air fluidized bed dryer. The time of the drying step S4 is not particularly limited and can be adjusted according to the water content and size of the coal.

In the dry distillation step S5, the coal dried in the drying step S4 is carbonized to obtain dry distillation coal. The dry distillation step S5 may be performed without performing the drying step S4. In this case, the water content of the coal is reduced at the initial stage of the carbonization step S5. In the carbonization step S5, carbonization coal having a temperature of, for example, 400 to 800 ° C., preferably 450 to 650 ° C. is obtained. By setting the dry distillation coal in such a temperature range, it is possible to sufficiently promote the semi-carbonization of biomass while sufficiently reforming the coal. The carbonization step S5 can be performed using a normal carbonization furnace such as a vertical shaft furnace, a coke oven, or a tunnel kiln furnace.

The changes in the properties of coal due to carbonization are shown below using lignite as an example. Table 1 shows an example of the properties of dry distillation coal obtained by heating brown coal at each temperature of 400 to 800 ° C. for 1 hour in an oxygen-free atmosphere using an electric furnace. Table 1 shows the results of industrial analysis, elemental analysis, and measurement of high calorific value of lignite before carbonization and carbonization obtained by carbonization at each temperature. As shown in Table 1, the amount of carbon in coal increases as the carbonization temperature rises and the volatile matter is desorbed, and the calorific value increases. There is a similar tendency not only in lignite but also in subbituminous coal.

The average particle size of the carbonized coal is preferably less than 50 mm, more preferably less than 30 mm, and even more preferably less than 10 mm. The average value of the particle size is the particle size at which the cumulative weight ratio when the crushed pieces of dry distillation coal are sieved and the particle size is distributed is 50%.

In the semi-carbonization step S6, dry distillation coal in a temperature range of 400 to 800 ° C. and biomass at room temperature (for example, 40 ° C. or lower) are mixed, and the biomass is semi-carbonized using the sensible heat of the dry distillation coal to obtain a biomass semi-carbonized product. A mixture containing dry distillation coal is obtained. When the biomass is mixed with the carbonization coal heated in the carbonization step S5, it is heated to a temperature of 200 to 450 ° C. (semi-carbonized temperature) from room temperature to become a biomass semi-carbonized product. The term "semi-carbonized" as used in the present disclosure refers to a state in which a part of biomass is carbonized by carbonization treatment, but is not completely carbonized, and there is still room for carbonization. The semi-carbonization step S6 can be performed in a state where contact with air is almost or completely cut off. As the equipment, for example, a vertical shaft furnace or a kiln may be used. By keeping the state of semi-carbonized without completely carbonizing, the yield of biomass semi-carbonized material (dry distillation product) can be sufficiently secured, and the amount of heat originally possessed by biomass can be fully utilized.

From the viewpoint of improving the pulverizability, the semi-carbonization temperature at the time of semi-carbonizing the biomass is preferably a temperature exceeding 200 ° C., more preferably 250 ° C. or higher, and further preferably 280 ° C. or higher. On the other hand, from the viewpoint of effectively utilizing the calorific value of biomass, the semi-carbonization temperature is preferably 400 ° C. or lower, more preferably 350 ° C. or lower.

The carbonization coal and biomass may be mixed so that the high calorific value of the molding fuel is 6000 [kcal / kg-dry] or more, or 6200 [kcal / kg-dry] or more. .. For example, the biomass may be mixed at a ratio of 1 to 80 parts by mass, or may be mixed at a ratio of 10 to 70 parts by mass with respect to a total of 100 parts by mass of the dry distillation coal and the biomass. As a result, it is possible to obtain a molded fuel that can achieve both a high calorific value and excellent combustibility at a high level. The temperature of the carbonization coal mixed with the biomass may be adjusted according to the mass ratio. The flammable gas and tar components generated by semi-carbonization of biomass may be recovered as fuel. This fuel may be used as a fuel in, for example, the carbonization step S5. Further, the surplus heat amount may be recovered as steam and effectively utilized.

By semi-carbonizing the biomass, the calorific value can be increased. The calorific value (high calorific value) of the biomass semi-carbide may be, for example, 5000 [kcal / kg-dry] or more, or 5,500 [kcal / kg-dry] or more. Based on the biomass before semi-carbonization, the higher calorific value of the biomass semi-carbide can be, for example, 1.1 times or more, preferably 1.2 times or more. By using such a biomass semi-carbide, a molded fuel having a high calorific value can be produced.

In the crushing step S7, the mixture containing the dry distillation coal and the biomass semi-carbide is crushed. The particle size after pulverization is preferably less than 10 mm, more preferably less than 5 mm, from the viewpoint of improving moldability. Biomass semi-carbide is more pulverizable than biomass before semi-carbonization. Therefore, the time and energy required for crushing can be reduced as compared with the case of crushing the biomass before semi-carbonization. Therefore, the molded fuel can be efficiently produced.

The bulk density of the biomass semi-carbide may be, for example, 0.1 to 0.5 g / cm ^3. The bulk density of the dry distillation coal may be, for example, 0.3 to 0.9 g / cm ^3. If dry distillation coal and biomass semi-carbide having different bulk densities are transported to a combustion facility as a mixture without being formed and put into the combustion facility, they are easily separated due to the difference in bulk density, and the calorific value is liable to fluctuate. In the production method of the present embodiment, by performing the following molding steps, it is possible to suppress the separation of the dry distillation coal and the biomass semi-carbide and suppress the fluctuation of the calorific value.

In the molding step S8, the molding raw material obtained by crushing the mixture in the crushing step S7 is molded to obtain a molding fuel. Examples of equipment for molding a molding raw material include a normal double roll molding machine and a uniaxial pressure molding machine. The shape of the molding fuel obtained by molding the molding raw material is not particularly limited, and may be, for example, a Massec type, a spherical shape, a columnar shape, an almond type, or a prismatic shape. The average particle size of the molded fuel is preferably 5 mm or more, more preferably 10 mm or more, from the viewpoint of improving handleability. The average value of the particle size is the particle size at which the integrated weight ratio when the molded fuel is sieved and the particle size is distributed is 50%. The density of the molded fuel may be, for example, 0.7 to 1.5 g / ml. The molding pressure is, for example, 0.5 to 10 ton / cm in linear pressure and, for example, 20 to 390 MPa in surface pressure.

In order to improve the moldability and the strength of the molding fuel, a binder may be blended with a mixture (crushed product) of carbonization coal and biomass semi-carbide to use as a molding raw material. As the binder, for example, polyvinyl alcohol can be used. This makes it possible to produce a molded fuel having excellent strength and water resistance.

In the above-mentioned production method, since the biomass is semi-carbonized by the sensible heat of the carbonization in the semi-carbonization step S6, it is possible to efficiently produce a molded fuel having a high calorific value with less energy loss. Further, since the carbonization step S5 is performed, the calorific value of the molded fuel can be increased as compared with the case where coal is used as it is.

Further, in the above-mentioned production method, the molding fuel is produced by the molding step S8 for molding the molding raw material obtained by crushing the mixture containing the dry distillation coal and the biomass semi-carbohydrate. The manufacturing method having such a molding step S8 has a handleability as compared with a method of simply mixing and burning biomass or biomass semi-carbide and coal or carbonization coal, and a method of separately charging these into a combustion facility. Excellent for.

The strength of the molded fuel can be quantified as the crushing strength measured using the measuring device 10 shown in FIG. As a sample, a columnar (diameter 15 mm × height 15 mm) molding fuel 16 is prepared. The molding fuel 16 is arranged on the support plate 17 arranged on the bottom plate of the gantry 18 so that the peripheral surface of the molding fuel 16 to be measured and the upper surface of the support plate 17 are in contact with each other. Then, the movable plate 14 attached to the gantry 18 is lowered so as to be able to move up and down, and the molding fuel 16 is sandwiched between the movable plate 14 and the support plate 17. Then, by operating the movable plate 14, a load is applied in the radial direction of the molding fuel 16. The crushing strength is obtained from the load when the molded fuel 16 finally breaks.

When an aqueous solution of polyvinyl alcohol is used as the binder aqueous solution in the molding step S8, a drying step of drying the molded product using, for example, an electric furnace or a dryer to reduce the water content may be performed after the molding step S8. .. Molding fuel may be obtained by drying the molded product. Drying may be carried out, for example, in the air at 60 to 100 ° C. or in an atmosphere of an inert gas for 30 minutes to 20 hours. Further, it may be carried out in the exhaust gas of the combustion furnace. By such drying, the water content of the molded fuel is preferably reduced to 5% by mass or less. With such a water content, hydrogen bonds between polyvinyl alcohol molecules (hydroxyl groups) are sufficiently promoted, and the strength of the molded fuel can be further increased. The moisture content of the molding fuel can be measured by a heat drying method (a method of measuring the mass before and after heat drying) using a moisture measuring machine.

The crushing strength of the molded fuel after the drying step is preferably 100 N or more, more preferably 150 N or more. The crushing strength of the molded fuel after being immersed in water at 20 ° C. for 24 hours is preferably 40 N or more, more preferably 50 N or more. As described above, the molding fuel of the present embodiment can maintain high strength not only when it is dried but also when it gets wet with water by using polyvinyl alcohol as a binder, for example.

The polyvinyl alcohol used as the binder used in the molding step S8 has a saponification degree of 99 mol% or more, preferably 99.3 mol% or more, more preferably more than 99.3 mol%, still more preferably more than 99.8 mol% (PVA). ) May be an aqueous solution. The degree of saponification represents the ratio of units that are actually saponified to vinyl alcohol units among the units that can be converted into vinyl alcohol units by saponification. The degree of saponification can be measured by the neutralization titration method according to JIS K 6726-1994. Specifically, a phenolphthalein solution is added to polyvinyl alcohol, and sodium hydroxide is added dropwise until it turns light red. The residue (residual acetic acid group) is obtained from the dropping amount, and the saponification degree is calculated.

That is, the saponification degree is calculated by a mathematical formula of n / (m + n) × 100 in polyvinyl alcohol having a molecular structure as shown in the following formula (1). The partially saponified polyvinyl alcohol has a molecular structure as shown in the following formula (1), whereas the fully saponified polyvinyl alcohol has most of the acetic acid groups substituted with hydroxyl groups as shown in the following formula (2). ..

When polyvinyl alcohol having a saponification degree of 99 mol% or more is dried, the hydroxyl groups of each molecule are firmly bonded to each other by hydrogen bonds. Once such a bond is formed, it does not easily dissociate when it comes into contact with water again. Therefore, the molding fuel obtained by molding using a binder containing an aqueous solution of polyvinyl alcohol having a saponification degree of 99 mol% or more is excellent in water resistance. The saponification degree of polyvinyl alcohol is preferably 99.3 mol% or more, more preferably 99.3 mol% or more, and further preferably 99.8 mol% or more, from the viewpoint of further increasing the strength of the molded fuel.

Commercially available products can be used as polyvinyl alcohol. The degree of polymerization of polyvinyl alcohol is preferably 1700 or more, more preferably 2500 or more, still more preferably 3300 or more, particularly from the viewpoint of improving the strength of the molded fuel during drying. The degree of polymerization of polyvinyl alcohol can be measured by a solution viscosity measuring method according to JIS K6726-1994.

The content of polyvinyl alcohol in the aqueous solution of polyvinyl alcohol is preferably 1 to 10% by mass, more preferably 2 to 10% by mass. As a result, it becomes easy to knead with the powdery molding raw material, and the dispersibility can be improved. Therefore, the uniformity of the molding raw material can be improved, and the variation in the strength of the molding fuel can be reduced.

The binder aqueous solution is superior in safety to the binder composed only of combustible materials. Further, since the molding raw material and the binder can be kneaded at room temperature without heating, even dry distillation coal having spontaneous ignition can be sufficiently and safely kneaded. However, it does not exclude heating and kneading.

The molding raw material can be prepared by mixing and kneading a mixture of dry distillation coal, a biomass semi-carbide, and an aqueous solution of polyvinyl alcohol. Depending on the viscosity of the aqueous solution of polyvinyl alcohol or the content of polyvinyl alcohol in the aqueous solution, water may also be blended and kneaded. The mixing ratio of the aqueous solution of polyvinyl alcohol to 100 parts by mass of the powdery mixture may be, for example, 5 to 50 parts by mass, and 5 to 30 parts by mass, from the viewpoint of making both moldability and kneadability sufficiently high. It may be a department.

From the viewpoint of sufficiently increasing the strength of the molding fuel, the content of polyvinyl alcohol in the molding fuel is preferably 0.5% by mass or more, more preferably 1.5% by mass or more. On the other hand, from the viewpoint of reducing the production cost of the molding fuel, the content of polyvinyl alcohol in the molding raw material is preferably 10% by mass or less. The water content in the molding raw material is preferably 20 to 40% by mass from the viewpoint of making both the moldability and the kneadability at a sufficiently high level.

The binder may contain components other than polyvinyl alcohol and water. Such components may be water-soluble. As the water-soluble one, α-starch is preferable from the viewpoint of production cost. Since α-starch is usually cheaper than polyvinyl alcohol, it is possible to reduce the production cost of the molded fuel by substituting a part of polyvinyl alcohol with α-starch. Further, when α-starch is used, the strength of the molded fuel at the time of drying can be sufficiently increased. In the molding fuel, the compounding ratio of α-starch to 100 parts by mass of the mixture is preferably 1 to 9 parts by mass from the viewpoint of sufficiently increasing the strength at the time of drying while maintaining water resistance.

In the modification of the above-described embodiment, a mixture containing dry distillation coal and biomass semi-carbide is provided between the semi-carbonization step S6 and the molding step S8, for example, in a temperature range of 140 ° C. or higher and 240 ° C. or lower, preferably 160 ° C. It has an oxidation treatment step of performing an oxidation treatment in a temperature range of ° C. or higher and 200 ° C. or lower. The oxidation treatment step may be performed before the pulverization step S7 or after the pulverization step S7. When the oxidation treatment is performed in such a temperature range, the functional groups on the surface of the carbonized coal are oxidized and the oxygen content is increased. In this way, the surface components of the carbonization coal are oxidized to stabilize the surface state, so that the self-heating property is reduced and the pyrophoricity is suppressed. In addition, oxidative decomposition associated with the oxidation treatment is suppressed, and the yield of the molded fuel can be increased.

In the oxidation treatment step, the time for oxidizing the mixture in the above temperature range is preferably 60 minutes or less. Thereby, the yield of the molded fuel can be sufficiently increased.

The atmosphere of the oxidation treatment step is not particularly limited as long as it contains oxygen, and may be air or a mixed atmosphere of an inert gas such as nitrogen and oxygen. Further, it may be the exhaust gas of the combustion furnace. The oxygen concentration may be, for example, 2 to 13% by volume or 3 to 10% by volume from the viewpoint of safety and efficiency of the oxidation treatment. This "volume%" is the volume ratio under the conditions of the standard state (25 ° C., 100 kPa).

In the oxidation treatment step, the functional groups on the surface of the carbonized coal are oxidized. As a result, self-heating due to oxidation is reduced, and it is possible to produce a molded fuel in which spontaneous ignition is sufficiently suppressed. The volatile content (VM) of the molded fuel may be 5% by mass or more or 10% by mass or more from the viewpoint of increasing the usefulness as a fuel. On the other hand, the volatile content (VM) of the molded fuel may be 30% by mass or less, or 25% by mass or less, from the viewpoint of further reducing the pyrophoricity. The volatile content in the present specification is an anhydrous base value measured in accordance with JIS M 8812: 2006 “Square electric furnace method”.

FIG. 3 is a flowchart of a molding fuel manufacturing method according to another embodiment. This production method includes a coarse crushing step S1 for coarsely crushing biomass, a drying step S2 for drying biomass, a crushing step S3 for crushing coal, a drying step S4 for drying coal, and carbonization of coal. A dry distillation step S5 for obtaining It has a molding step S8 for obtaining fuel. The rough crushing step S1, the drying step S2, the crushing step S3, the drying step S4, the drying distilling step S5, and the molding step S8 can be performed in the same manner as in the above-described embodiment. Therefore, the description of the above-described embodiment can be applied.

In the semi-carbonization step S6', the biomass may be semi-carbonized using another heat source instead of the sensible heat of the carbonization coal. Further, the sensible heat of the carbonization coal may be used as a part of the heat source. Biomass semi-carbide is obtained by heating the biomass to a temperature of 200-450 ° C (semi-carbide temperature). Similar to the semi-carbonization step S6, the semi-carbonization step S6'can also be performed in a state where contact with air is almost or completely blocked. As the equipment, for example, a vertical shaft furnace or a kiln may be used. In the modified example, the semi-carbonization of a part of the biomass may be performed by using the sensible heat of the carbonization coal, and the semi-carbonization of the remaining biomass may be performed by using another heat source. This enables flexible operation.

In the crushing step S7', the biomass semi-carbide is crushed. The particle size after pulverization is preferably less than 10 mm, more preferably less than 5 mm, from the viewpoint of improving moldability. Biomass semi-carbide is more pulverizable than biomass before semi-carbonization. Therefore, the time and energy required for crushing can be reduced as compared with the case of crushing the biomass before semi-carbonization. Therefore, the molded fuel can be efficiently produced.

In the molding step S8, the biomass semi-carbide may be mixed at a ratio of 1 to 80 parts by mass with respect to a total of 100 parts by mass of the dry distillation coal and the biomass semi-carbide, and the biomass semi-carbide may be mixed at a ratio of 10 to 70 parts by mass. It may be mixed. As a result, it is possible to obtain a molded fuel that can achieve both a high calorific value and excellent combustibility at a high level.

In the modified example of the above-described embodiment, before the molding step S8, the mixture obtained by mixing the dry distillation coal and the biomass semi-carbide is prepared, for example, in a temperature range of 140 ° C. or higher and 240 ° C. or lower, preferably 160 ° C. or higher. Moreover, the oxidation treatment step of performing the oxidation treatment in the temperature range of 200 ° C. or lower may be performed.

The oxidation treatment step may be performed between the semi-carbonization step S6'and the crushing step S7', or the biomass semi-carbide and the dry distillation coal are individually oxidized before being mixed with the dry distillation coal and the biomass semi-carbide. You may. In the oxidation treatment step, the time for oxidation treatment in the above temperature range is preferably 60 minutes or less. Thereby, the yield of the molded fuel can be sufficiently increased.

The atmosphere of the oxidation treatment step is not particularly limited as long as it contains oxygen, and may be air or a mixed atmosphere of an inert gas such as nitrogen and oxygen. Further, it may be the exhaust gas of the combustion furnace. The oxygen concentration may be, for example, 2 to 13% by volume or 3 to 10% by volume from the viewpoint of safety and efficiency of the oxidation treatment. This "volume%" is the volume ratio under the conditions of the standard state (25 ° C., 100 kPa).

When the biomass semi-carbide and the dry distillation coal are individually oxidized before being mixed, the oxidation treatment of the dry distillation coal may be carried out at 160 ° C. or higher and 240 ° C. or lower, or 160 ° C. or higher and 220 ° C. or lower. The oxidation treatment of the biomass semi-carbide may be carried out at 100 ° C. or higher and lower than 200 ° C., or 130 ° C. or higher and 180 ° C. or lower. Biomass semi-carbide can be sufficiently improved in safety even if it is oxidized at a temperature lower than that of carbonized coal.

In the production method of each of the above embodiments, low-grade coal such as lignite and subbituminous coal and biomass are used as raw materials, but have a calorific value equal to or higher than that of steam coal for coal-fired power generation, and by mixing biomass. Molded fuel with low CO ₂ emissions can be produced at low cost.

One embodiment of the molded fuel of the present disclosure can be produced, for example, by the production method of each of the above-mentioned embodiments or modifications thereof. Therefore, the above description of the manufacturing method also applies to molded fuels. The molding fuel may include a pulverized mixture of carbonized coal and biomass semi-carbide. Such molded fuel is excellent in handleability. Coal may include at least one of lignite and subbituminous coal. Thereby, the calorific value of the molded fuel can be sufficiently increased. The content ratio of carbonization coal and biomass semi-carbide may be such that the calorific value of the molding fuel is 6000 [kcal / kg-dry] or more on an anhydrous basis, and 6200 [kcal / kg-dry] or more on an anhydrous basis. The ratio may be.

The molding fuel may be obtained by molding a molding raw material containing the above-mentioned pulverized product and an aqueous binder solution. The binder aqueous solution may be an aqueous solution containing polyvinyl alcohol having a saponification degree of 99 mol% or more. By containing such polyvinyl alcohol, it is possible to improve the water resistance while sufficiently increasing the crushing strength of the molded fuel.

The crushing strength of the molded fuel after drying is preferably 100 N or more, more preferably 150 N or more. The crushing strength of the molded fuel after being immersed in water at 20 ° C. for 24 hours is preferably 40 N or more, more preferably 50 N or more. Here, the crushing strength of 50 N is such that it does not break even if its own weight is applied to the molded fuel at the bottom when it is piled up in the yard with a pile height of 15 m, and it can suppress pulverization during transportation. Strength.

The molding fuel according to one embodiment has a calorific value equal to or higher than that of steam coal for coal-fired power generation while using low-grade coal such as lignite and subbituminous coal and biomass as raw materials, and CO by mixing biomass. ₂ Emissions can be reduced.

When the molding fuel is immersed in 13 times the mass of water at 25 ° C. for 2 days, the COD of the water may be 500 mass ppm or less, 400 mass ppm or less, and 300 mass ppm or less. May be good. This makes it possible to sufficiently reduce the impact on the environment, for example, when the product is piled up in the yard. From the same viewpoint, when immersed in water under the same conditions, the turbidity of the water may be 200 degrees or less, or 100 degrees or less. From the same viewpoint, when immersed in water under the same conditions, the oil content in the water may be 1 wt ppm or less.

Since the molded fuel contains dry distillation coal, it has a high calorific value. Moreover, since it contains biomass semi-carbide, it has a small fuel ratio (fuel ratio = fixed carbon (FC) / volatile matter (VM)). When the fuel ratio is small, the volatile content is high, so that the ignitability is high, and the volatile content is removed immediately after the start of combustion, so that the molded fuel becomes porous and the specific surface area becomes large. Therefore, the molded fuel is also excellent in combustibility. In addition, the amount of unburned components and harmful substances such as nitrogen oxides can be reduced. The molded fuel may be processed into an arbitrary size and used as a solid fuel. Further, the molding fuel may be mixed with other granules to obtain a solid fuel.

The content of the biomass semi-carbide in the molding fuel may be 1 to 80 parts by mass or 10 to 70 parts by mass with respect to 100 parts by mass of the total of the dry distillation coal and the biomass semi-carbide. This makes it possible to achieve both a high calorific value and excellent combustibility at a high level.

Although some embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. For example, in the molding fuel production method, the coarse crushing step S1 and the crushing step S3 may not be performed depending on the sizes of biomass and coal. Further, drying may be performed in the dry distillation step S5 or the semi-carbonization step S6, S6'without performing the drying steps S2 and S4.

The contents of the present disclosure will be described in more detail with reference to the experimental results.

(Preliminary experiment)
[Changes in biomass due to semi-carbonization]
Eucalyptus chips (particle size: 10 to 50 mm) were prepared as biomass. This biomass was heated in an oxygen-free atmosphere at a temperature of 200 to 400 ° C. for 2 hours using an electric furnace to obtain a biomass semi-carbide. Industrial analysis, elemental analysis and higher calorific value of biomass before semi-carbonization and biomass semi-carbonized obtained by semi-carbonization at each semi-carbonization temperature were measured. The results are as shown in Table 2.

In FIG. 4, the calorific value (higher calorific value) of the biomass semi-carbide shown in Table 2 based on anhydrous is plotted. From these results, it was confirmed that the calorific value can be increased by semi-carbonizing the biomass.

The Hardgrove Grindability Index (HGI) of biomass and biomass semi-carbide was measured according to JIS M 8801. The results were as shown in FIG. In FIG. 5, the plot at a semi-carbonized temperature of 25 ° C. shows the results of biomass before semi-carbonization. As shown in FIG. 5, it was confirmed that the biomass semi-carbide is more easily crushed than the biomass. A typical coal has a Hardgrove Grindability Index (HGI) of 30-70 (the region between the two solid lines in FIG. 5). From these results, it was confirmed that when the semi-carbonized temperature is 200 ° C. or higher, the biomass semi-carbide can have pulverizability equal to or higher than that of coal.

(Experimental Example 1)
A mixture was obtained by mixing the biomass semi-carbide (semi-carbide temperature: 320 ° C.) in Table 2 and the carbonization coal obtained by carbonizing coal at 480 ° C. for 60 minutes. The mixing ratio was 30 parts by mass for the biomass semi-carbide and 70 parts by mass for the dry distillation coal with respect to 100 parts by mass in total of the biomass semi-carbide and the dry distillation coal. The average particle size of both the biomass semi-carbide and the carbonization coal was 0.2 mm. A molding raw material was obtained by mixing the mixture, an aqueous solution (binder aqueous solution) containing a commercially available polyvinyl alcohol (saponification degree:> 99.85 mol%, degree of polymerization: 1700) at a concentration of 10% by mass, and water. At this time, a plurality of molding raw materials were prepared by changing the blending ratio in the range of 10 to 40 parts by mass (1 to 4 parts by mass as a binder) with respect to 100 parts by mass of the mixture.

Each molding raw material was molded using a uniaxial pressure molding machine (molding pressure: 283 MPa) to prepare a cylindrical (diameter 15 mm × height 15 mm) molding fuel. The produced molded fuel was dried in air at 80 ° C. for 15 hours. The moisture content after drying was measured by a heat-drying method using a commercially available moisture measuring machine, and found to be 2% by mass in each case. The crushing strength of the molded fuel after drying was measured using the measuring device shown in FIG. The measurement results are as shown in Table 3 (after drying) and FIG. 6 (black circles). The remarks in Table 3 show the types of Examples and Comparative Examples.

Each of the dried molding fuels was immersed in water at about 20 ° C. for 24 hours. Then, the molded fuel was taken out from the water, and the crushing strength was measured using the measuring device shown in FIG. The measurement results are as shown in Table 3 (after immersion in water) and FIG. 6 (black triangles in FIG. 6). It was confirmed that by using polyvinyl alcohol as a binder, the strength after immersion in water can be sufficiently increased, and a molded fuel exceeding the target strength (40 N or more) can be produced even after immersion in water.

As shown in FIG. 6, it was confirmed that the crushing strength can be increased by increasing the compounding ratio of polyvinyl alcohol.

(Experimental Example 2)
A mixture was obtained by mixing the biomass semi-carbide (320 ° C.) shown in Table 2 with the carbonized coal obtained by carbonizing coal at 480 ° C. for 60 minutes. The mixing ratio was 50 parts by mass for the biomass semi-carbide and 50 parts by mass for the dry distillation coal with respect to 100 parts by mass in total of the biomass semi-carbide and the dry distillation coal.

The mixture was heated at a temperature of 180 ° C. for 60 minutes in an atmosphere with an oxygen concentration of 5% by volume. A mixture (mixed fuel) was obtained by performing such an oxidation treatment step (dry distillation coal: biomass semi-carbide = 50 parts by mass: 50 parts by mass). An oxidation calorific value measurement test (DSC test) of the prepared mixed fuel was carried out. In this test, 10 mg of mixed fuel crushed to 212 μm or less was placed in an alumina sample container, the sample temperature was raised to 107 ° C under a nitrogen atmosphere, and after reaching 107 ° C, the atmosphere was switched to air to generate heat of the sample. The time course of the amount was examined. The results are as shown in the curve (solid line 1) in FIG.

For comparison, FIG. 7 shows the evaluation results of the mixture not subjected to the oxidation treatment step (single-dot chain line 2) and the evaluation results of coal (subbituminous coal and bituminous coal) (subbituminous coal: broken line 3, bituminous coal: two-dot chain line 4). Indicated. As shown in FIG. 7, it was confirmed that the oxidation treatment of the mixture makes it difficult to generate heat and improves the safety.

A DSC test was conducted on carbonized coal and biomass semi-carbide used as raw materials for the mixed fuel, oxidized products obtained by oxidizing these, and coal (subbituminous coal and bituminous coal). The results are as shown in FIG. In FIG. 8, the solid line 1 shows the carbonization coal after the oxidation treatment, and the solid line 2 shows the carbonization coal before the oxidation treatment. The alternate long and short dash line 3 shows the biomass semi-carbide after the oxidation treatment, and the alternate long and short dash line 4 shows the biomass semi-carbide before the oxidation treatment. The dashed line 5 indicates sub-bituminous coal, and the dashed line 6 indicates bituminous coal.

The oxidation treatment of the biomass semi-carbide was carried out by heating at a temperature of 160 ° C. for 60 minutes in an atmosphere having an oxygen concentration of 5% by volume. The oxidation treatment of the dry distillation coal was carried out by heating at a temperature of 220 ° C. for 40 minutes in an atmosphere having an oxygen concentration of 5% by volume. From the results shown in FIG. 8, it was confirmed that the safety of the dry distillation coal and the biomass semi-carbide was improved by performing the oxidation treatment.

(Experimental Example 3)
When the total of the biomass semi-carbide (semi-carbide temperature: 320 ° C.) and the dry-distilled coal obtained by carbonizing brown coal at 480 ° C for 60 minutes in Table 2 is 100 parts by mass, the biomass semi-carbide is 1 Multiple mixtures were obtained by mixing at a ratio of ~ 80 parts by mass. Table 4 summarizes the industrial analysis, elemental analysis, and high calorific value of the molded fuel obtained by molding each of these mixtures. Since the calorific value of steaming coal used for coal-fired power generation is usually 6,000 [kcal / kg-dry] or more, even molding fuel obtained by mixing dry distillation coal and biomass semi-carbide is generally used. It was confirmed that the calorific value equivalent to that of charcoal can be achieved.

The coal carbonization temperature, biomass semi-carbonization temperature, and mixing ratio of Experimental Examples 1 and 2 are examples. By adjusting these, for example, a molded fuel having an arbitrary calorific value of 6,000 [kcal / kg-dry] or more and 7,900 [kcal / kg-dry] or less can be produced. The mixing ratio of the biomass semi-carbide can also be changed as appropriate.

Table 4 shows the results of the industrial analysis of molded fuel and the CO ₂ emissions when it is used in thermal power generation. _{The CO 2} emission amount when coal and biomass are co-fired at a calorific value ratio of 3% without semi-carbonizing the conventional biomass is about 0.838 kg-CO ₂ / kWh. _{On the other hand, as shown in Table 4, CO 2} emissions can be significantly reduced by increasing the mixing ratio of the biomass semi-carbide in the molding fuel. Further, increasing the mixing ratio of the biomass semi-carbide increases the volatile matter (VM) and improves the flammability.

(Experimental Example 4)
A mixture was obtained by mixing the biomass semi-carbide (320 ° C.) shown in Table 2 with the carbonized coal obtained by carbonizing coal at 480 ° C. for 60 minutes. The mixing ratio was 50 parts by mass for the biomass semi-carbide and 50 parts by mass for the dry distillation coal with respect to 100 parts by mass in total of the biomass semi-carbide and the dry distillation coal.

This mixture, the aqueous binder solution used in Experimental Example 1, and water were mixed to obtain a molding raw material. The blending ratio at this time was 30 parts by mass (3 parts by mass as a binder) of the aqueous binder solution and 10 parts by mass of water with respect to 100 parts by mass of the mixture. The molding raw material was molded using a double roll molding machine to prepare an almond-shaped molding fuel (length x width x height = 24 mm x 16 mm x 13 mm). The produced molded fuel was dried in the air for 5 hours in the sun. The molding pressure was 3 t / cm. The weight of the molded fuel after drying was 135 g, and the water content was about 7% by mass (Example 1). In addition to the above molding raw materials, a biomass semi-carbide (semi-carbide temperature: about 300 ° C., calorific value: about 5000 kcal / kg-dry) was prepared. The mass of the biomass semi-carbide was 135 g (Reference Example 1).

The molding fuel of Example 1 and the biomass semi-carbide of Reference Example 1 were immersed in water 13 times their respective masses and allowed to stand at 25 ° C. for 48 hours. After standing, the solid content was removed from the water using a sieve having a mesh size of 0.5 mm. The oil content, chemical oxygen demand (COD) and turbidity of the water (eluted water) thus obtained were measured. The oil content was measured as the amount of normal hexane extract. The turbidity was measured according to JIS K0101 "Industrial water test method". The measurement method was a transmitted light method, and kaolin was used as the turbidity standard solution. The chemical oxygen demand (COD) was measured by the acidic high temperature permanganate method (COD _{Mn) with potassium permanganate.} The results are shown in Table 5. Table 5 also shows the analytical values of water before immersing the molding raw material as blanks.

The turbidity and COD of the molded fuel of Example 1 were about 10% of the biomass semi-carbide of Reference Example 1. It was confirmed that the molded fuel of Example 1 can sufficiently reduce the impact on the environment as compared with Reference Example 1 even if it is stored in the yard in the open.

(Experimental Example 5)
[Use of molded fuel]
<Example 2>
The biomass semi-carbide (320 ° C.) in Table 2 and the carbonized coal obtained by carbonizing coal at 480 ° C. for 60 minutes were each oxidized. The oxidation treatment of the biomass semi-carbide was carried out by heating at a temperature of 160 ° C. for 60 minutes in an atmosphere having an oxygen concentration of 5% by volume. The oxidation treatment of the dry distillation coal was carried out by heating at a temperature of 220 ° C. for 40 minutes in an atmosphere having an oxygen concentration of 5% by volume.

The oxidized biomass semi-carbide and the oxidized dry distillation coal were mixed to obtain a mixture. The mixing ratio was 50 parts by mass for the biomass semi-carbide and 50 parts by mass for the dry distillation coal with respect to 100 parts by mass in total of the biomass semi-carbide and the dry distillation coal. The mixture, the aqueous binder solution used in Experimental Example 1, and water were mixed to obtain a molding raw material. The blending ratio at this time was 35 parts by mass (3.5 parts by mass as a binder) for the aqueous binder solution and 5.5 parts by mass for water with respect to 100 parts by mass of the mixture.

The molding raw material was molded using a double roll molding machine to prepare an almond-shaped molding fuel (length x width x height = 24 mm x 16 mm x 13 mm). The produced molded fuel was dried in the air for 5 hours in the sun. The molding pressure was 3 t / cm. The molded fuel was crushed with a mill to obtain a crushed product having a particle size of 1 to 220 μm. This crushed product was mixed with bituminous coal to prepare a solid fuel for testing. The mass ratio of the crushed product of the molded fuel to the solid fuel was set to 30%. This was used as the solid fuel of Example 2.

<Example 3>
The mixing ratio of the oxidized biomass semi-carbohydrate and the oxidized dry-distilled coal was 100 parts by mass of the total of the biomass semi-carbohydrate and the dry-distilled coal, 30 parts by mass of the biomass semi-carbohydrate, and 70 parts by mass of the dry-distilled coal. Except for the above, a solid fuel for testing was prepared in the same manner as in Example 2. This was used as the solid fuel of Example 3.

<Example 4>
In addition to the eucalyptus chips used in the preliminary experiment, pine chips and construction waste were prepared. Eucalyptus chips: Pine chips: Construction waste materials = 7: 7: 6 were mixed in a mass ratio to obtain biomass. This biomass was heated at 320 ° C. for 2 hours in an oxygen-free atmosphere to obtain a biomass semi-carbide. A solid fuel was prepared in the same manner as in Example 2 except that this biomass semi-carbide was used.

<Example 5>
Biomass semi-carbide was obtained by the same procedure as in Example 4. A solid fuel was prepared in the same manner as in Example 3 except that this biomass semi-carbide was used.

<Reference example 2>
Bituminous coal (wambo charcoal) was prepared. This was crushed with a mill to obtain the solid fuel of Reference Example 2.

[Combustion test]
A combustion test was conducted by supplying the solid fuel of Examples 2 to 5 and the bituminous coal of Reference Example 2 to the two-stage combustion type test apparatus shown in FIG. Solid fuel was supplied to the burner 30 of the test apparatus from the inlet 30a, and primary air was supplied from the air supply pipe 31. Further, secondary air was supplied from the air supply pipe 32 to the main body 40 of the combustion device. The supply ratio of the primary air and the secondary air was 7: 3. The main body 40 of the combustion device is provided with five secondary air supply ports (supply ports 41, 42, 43, 44, 45).

A combustion test was conducted using the supply ports 41, 42, 43, 44, and 45 individually, and the unburned content and NOx concentration of the combustion exhaust gas discharged from the exhaust port 48 were measured. The measurement results of unburned matter and nitrogen oxide (NOx) concentration when each supply port is used are shown in Tables 6 and 7, respectively. The unburned content and NOx were measured by thermogravimetric analysis and infrared absorption method.

As shown in Table 6, in Examples 2 to 5, the unburned content could be reduced as compared with the case where bituminous coal was used. FIG. 10 is a graph showing the relationship between the unburned content and the NOx concentration. Curve 1 shows the result of Reference Example 2, curve 2 shows the result of Example 2, curve 3 shows the result of Example 3, curve 4 shows the result of Example 4, and curve 5 shows the result of Example 5. From the results of FIG. 10, it was confirmed that, when compared with the same unburned content, Examples 2 to 5 (Curves 2 to 5) can reduce the amount of NOx generated as compared to Reference Example 2 (Curves 1).

[Evaluation of spontaneous exothermic reaction]
The spontaneous combustion property of the solid fuel of Examples 2 to 5 and the bituminous coal of Reference Example 2 was evaluated by using an adiabatic measurement method (R70 method) for evaluating the spontaneous combustion property of coal from 40 ° C. to 70 ° C. Specifically, 200 g of a sample was filled in a reaction vessel, and the reaction vessel was placed in a constant temperature bath at 40 ° C. A gas supply unit that supplies air at the same temperature as the temperature of the sample in the reaction vessel was connected to the reaction vessel. The temperature rise curve of the sample in the reaction vessel was measured.

FIG. 11 is a graph showing the temperature rise curves of the solid fuels of Examples 2 to 5 and the bituminous coal of Reference Example 2 by the R70 method. Curve 1 shows the result of Reference Example 2, curve 2 shows the result of Example 2, curve 3 shows the result of Example 3, curve 4 shows the result of Example 4, and curve 5 shows the result of Example 5. As shown in FIG. 11, it was confirmed that the solid fuels of Examples 2 to 5 have suppressed spontaneous heat generation and are excellent in safety as compared with the bituminous coal of Reference Example 2.

10 ... Measuring device, 14 ... Movable plate, 16 ... Molded fuel, 17 ... Support plate, 18 ... Stand, 30 ... Burner, 31, 32 ... Air supply pipe, 40 ... Main body, 41, 42, 43, 44, 45 … Supply port, 48… exhaust port.

Claims (14)

A carbonization step of carbonizing coal containing at least one of lignite and subbituminous coal to obtain carbonization.
A method for producing a molding fuel, comprising a molding step of molding a mixture containing the dry distillation coal and a biomass semi-carbide obtained by semi-carbonizing the biomass to obtain a molding fuel. The mixture has a semi-carbonization step of semi-carbonizing the biomass to obtain the biomass semi-carbide and a crushing step of crushing the biomass semi-carbide, and the crushed biomass semi-carbide and the dry distillation coal are mixed. The method for producing a molded fuel according to claim 1. It has an oxidation treatment step of oxidizing the dry distillation coal and the biomass semi-carbide, respectively.
The invention according to claim 1 or 2, wherein in the oxidation treatment step, the dry distillation coal is heated to a temperature range of 160 ° C. or higher and 240 ° C. or lower, and the biomass semi-carbide is heated to a temperature range of 100 ° C. or higher and lower than 200 ° C. Manufacturing method of molding fuel. The method for producing a molded fuel according to claim 1, further comprising a semi-carbonization step of semi-carbonizing the biomass using the sensible heat of the carbonization coal to obtain the mixture. The method for producing a molded fuel according to claim 1 or 4, further comprising a pulverizing step of pulverizing the mixture before the molding step. The molded fuel according to any one of claims 1, 4 and 5, wherein the biomass is heated to 200 to 450 ° C. and semi-carbonized by mixing with the dry distillation coal in a temperature range of 400 to 800 ° C. Manufacturing method. The method for producing a molded fuel according to any one of claims 1, 2, 4 to 6, further comprising an oxidation treatment step of oxidizing the mixture in a temperature range of 140 ° C. or higher and 240 ° C. or lower. Before semi-carbonizing the biomass
A coarse pulverization step of coarsely pulverizing the biomass so that the average value of the particle size of the biomass exceeds 7 mm and is less than 50 mm.
The method for producing a molded fuel according to any one of claims 1 to 7, further comprising a drying step of drying the coarsely pulverized biomass. The method for producing a molding fuel according to any one of claims 1 to 8, wherein in the molding step, a binder containing polyvinyl alcohol having a saponification degree of 99 mol% or more is used. The method for producing a molded fuel according to claim 9, wherein the degree of polymerization of polyvinyl alcohol is 1700 or more. The method for producing a molded fuel according to any one of claims 1 to 10, wherein the COD of the water is 500 mass ppm or less when immersed in water 13 times the mass of the molded fuel at 25 ° C. for 2 days. Molded fuel containing carbonized coal and biomass semi-carbide of coal containing at least one of lignite and subbituminous coal. The molded fuel according to claim 12, which comprises polyvinyl alcohol having a saponification degree of 99 mol% or more. The molded fuel according to claim 12 or 13, wherein the COD of the water is 500 mass ppm or less when immersed in 13 times the mass of water at 25 ° C. for 2 days.

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