CN111630140A

CN111630140A - Shaped fuel and method for producing same

Info

Publication number: CN111630140A
Application number: CN201980009088.4A
Authority: CN
Inventors: 森英一朗; 武田卓; 小胁幸男; 犬丸哲朗
Original assignee: Kyushu Electric Power Co Inc; Nippon Steel and Sumikin Engineering Co Ltd
Current assignee: Kyushu Electric Power Co Inc; Nippon Steel Engineering Co Ltd
Priority date: 2018-09-27
Filing date: 2019-09-26
Publication date: 2020-09-04
Also published as: JP6910546B2; AU2019347405B2; WO2020067384A1; JPWO2020067384A1; AU2019347405A1

Abstract

Provided is a method for producing a molded fuel, which comprises the steps of: a carbonization step of carbonizing coal containing at least one of lignite and subbituminous coal to obtain carbonized coal; and a molding step of molding a mixture containing the carbonized coal and a biomass half-carbide obtained by half-carbonizing the biomass to obtain a molded fuel. Provided is a briquette fuel containing carbonized coal and biomass semi-carbides of coal including at least one of lignite and subbituminous coal.

Description

Shaped fuel and method for producing same

Technical Field

The present invention relates to a formed fuel and a method for producing the same.

Background

In recent years, the price of coal as a power source for coal-fired power generation has increased due to an increase in power generation demand centered on emerging countries, and it is still uneasy to stabilize supply. Therefore, a technique has been studied in which low-quality coal such as lignite and subbituminous coal, which is inexpensive and can be collected in a large amount, is used as a substitute for coal-fired power generation power coal (for example, see patent document 1).

A large amount of CO can be discharged in coal thermal power generation₂Thus as a means of reducing CO in coal-fired power generation₂As a means for preventing global warming, a technique of co-firing biomass as a renewable energy source when coal is fired has been studied. Since biomass tends to have poor pulverizability and a small calorific value, when woody biomass is directly used for co-firing, the co-firing rate is limited to about 3% in terms of calorific ratio.

Therefore, patent document 2 proposes a technique of roasting biomass in order to improve the pulverization property. In addition, patent document 3 proposes a technique for roasting biomass in order to increase the heat of the biomass.

Patent documents

2 and 3 propose that a solid fuel obtained by calcining biomass is used by being mixed with coal.

The solid fuel may be stored in a storage, for example. As an index of safety of solid fuels, the R70 method for evaluating natural calorific properties of coal is known (see patent document 4 and non-patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-23280

Patent document 2: international publication No. 2014/050964

Patent document 3: japanese patent laid-open publication No. 2017-39933

Patent document 4: japanese patent laid-open publication No. 2019-066296

Non-patent document

Non-patent document 1: b. amine et al, Adiastic testing products for determining the self-describing compliance of the clock and sample using effects, Thermochimic Acta 362(2000)79-87

Disclosure of Invention

Problems to be solved by the invention

When low-quality coal such as brown coal or subbituminous coal is used as a substitute for power coal for coal-fired power generation, the calorific value of the low-quality coal is small, and therefore it is necessary to increase the calorific value of the substitute fuel to a value equivalent to the calorific value of the power coal. In addition, to reduce CO₂In the case of co-combustion of biomass, the biomass needs to be pulverized before being supplied to a combustion facility, and therefore, the biomass needs to be easily pulverized. Further, since biomass has a smaller calorific value than coal, a technique for increasing the calorific value to correspond to power coal is required.

When coal and a solid fuel derived from biomass are used by co-combustion in a combustion facility such as a boiler, the coal and the solid fuel derived from biomass need to be treated separately until they are supplied to the combustion facility. Further, if coal and a solid fuel obtained from biomass are mixed before being supplied to a combustion facility, the bulk density of the two fuels differs, and therefore, the mixing ratio varies greatly, and there is a concern that the supply heat fluctuates and the operation of the combustion facility becomes unstable.

Accordingly, the present invention provides a method for producing a shaped fuel, which can produce a shaped fuel having a high heat content and excellent handling properties while using a biomass having a bulk density different from that of coal. Also disclosed is a molded fuel which contains a biomass having a bulk density different from that of coal, has a high heat value, and is excellent in handling properties.

Means for solving the problems

A method for producing a molded fuel according to an aspect of the present invention includes the steps of: a carbonization step of carbonizing coal containing at least one of lignite and subbituminous coal to obtain carbonized coal; and a molding step of molding a mixture containing the carbonized coal and a biomass half-carbide obtained by half-carbonizing the biomass to obtain a molded fuel.

In the above production method, the carbonized coal having a high carbon component ratio and a high heat value is used in the carbonization step, and therefore, the heat value can be increased as compared with the case of using coal containing at least one of lignite and subbituminous coal. Further, since the molded fuel is produced by the molding step, the fuel is superior in handling property as compared with a fuel in which both are mixed without molding. Therefore, a formed fuel having a high heat capacity and excellent handling properties can be produced while using biomass. In addition, the formed fuel has a small fuel ratio (fuel ratio ═ Fixed Carbon (FC)/volatile component (VM)) because it contains biomass semi-carbides. When the fuel ratio is small, the volatile component is high and therefore rich in ignitability, and the volatile component disappears immediately after the start of combustion, whereby the formed fuel becomes porous and the specific surface area becomes large. This makes the fuel easy to burn and has excellent combustibility.

The above production method may further include a semi-carbonization step of semi-carbonizing biomass to obtain biomass semi-carbide, and a pulverization step of pulverizing the biomass semi-carbide, and the pulverized biomass semi-carbide may be mixed with the dry-distilled coal to obtain a mixture. Biomass semi-carbides are more easily comminuted than biomass. Therefore, the time and energy required for pulverization can be reduced. Therefore, the molded fuel can be efficiently produced.

The above production method may further include an oxidation treatment step of oxidizing the carbonized coal and the biomass semi-carbide, respectively. In the oxidation treatment step, the carbonized coal may be heated to a temperature range of 160 ℃ to 240 ℃ inclusive, and the biomass semi-carbide may be heated to a temperature range of 100 ℃ to less than 200 ℃. This oxidizes the surface components of the carbonized coal and biomass semi-carbides to stabilize the surface state, thereby reducing the self-heat property and suppressing the self-combustion property. Further, oxidative decomposition accompanying the oxidation treatment is suppressed, and the yield of the molded fuel can be improved.

The above production method may further include a semi-carbonization step of semi-carbonizing the biomass by utilizing sensible heat of the carbonized coal to obtain a mixture. In this production method, the sensible heat of the carbonized coal is utilized to semi-carbonize the biomass, so that the energy loss can be reduced and the biomass semi-carbide and the formed fuel can be efficiently produced.

The above-mentioned production method may further comprise a pulverization step of pulverizing the mixture before the molding step. Biomass semi-carbides are more easily comminuted than biomass. Therefore, the time and energy required for pulverization can be reduced. Therefore, the molded fuel can be produced more efficiently. The pulverization step may be performed between the semi-carbonization step and the molding step.

In the above production method, the biomass may be heated to 200 to 450 ℃ by mixing with the carbonized coal at a temperature in the range of 400 to 800 ℃ to semi-carbonize the biomass. This enables sufficiently efficient production of a biomass semi-carbide having both a high calorific value and good pulverizability. The temperature of the biomass mixed with the carbonized coal may be 150 ℃ or lower.

The production method may further include an oxidation treatment step of subjecting the mixture to an oxidation treatment at a temperature ranging from 140 ℃ to 240 ℃. This oxidizes the surface components of the carbonized coal and biomass semi-carbides to stabilize the surface state, thereby reducing the self-heat property and suppressing the self-combustion property. Further, oxidative decomposition accompanying the oxidation treatment is suppressed, and the yield of the molded fuel can be improved.

The method may further comprise the following steps before the biomass is semi-carbonized: a coarse pulverization step of coarsely pulverizing the biomass so that the average particle size of the biomass is greater than 7mm and less than 50 mm; and a drying step of drying the coarsely pulverized biomass. This can sufficiently progress the semi-carbonization of the biomass, and further improve the handleability.

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. In addition, when polyvinyl alcohol having a high saponification degree is dried, hydroxyl groups in each molecule are hydrogen-bonded to each other, and excellent water resistance is exhibited. That is, the molecules of polyvinyl alcohol contained as a binder in the fuel for molding are strongly bonded to each other, and thus high strength can be maintained even when wetted with water.

The polymerization degree of the polyvinyl alcohol is preferably 1700 or more. This can further improve the strength of the molded fuel particularly at the time of drying.

Preferably, the molded fuel obtained by the above production method has a COD of 500 ppm by mass or less when immersed in 13 times by mass of water at 25 ℃ for 2 days. This can sufficiently reduce the influence on the environment even when the stack is placed in the open air, for example.

One aspect of the invention relates to a shaped fuel comprising a carbonized coal and a biomass semi-carbide of coal comprising at least one of lignite and subbituminous coal. Since the briquette fuel contains the carbonized coal, the briquette fuel can be produced at a higher temperature than the briquette fuel containing the coal. Further, since the formed fuel contains the carbonized coal and the biomass semi-carbide, the fuel has excellent handling properties as compared with a fuel in which both are mixed without forming. In addition, the formed fuel has a small fuel ratio (fuel ratio ═ Fixed Carbon (FC)/volatile component (VM)) because it contains biomass semi-carbides. When the fuel ratio is small, the volatile component is high and therefore rich in ignitability, and the volatile component disappears immediately after the start of combustion, whereby the formed fuel becomes porous and the specific surface area becomes large. This makes the fuel easy to burn and has excellent combustibility.

The molded fuel may contain polyvinyl alcohol having a saponification degree of 99 mol% or more. This can sufficiently improve the compressive strength of the molded fuel and also improve the water resistance.

Preferably, the COD of the formed fuel is 500 mass ppm or less when the fuel is immersed in 13 times the mass of water at 25 ℃ for 2 days. This can sufficiently reduce the influence on the environment even when the stack is placed in the open air, for example.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a method for producing a shaped fuel, which can produce a shaped fuel having a high heat content and excellent handling properties while using a biomass having a bulk density different from that of coal. Further, a formed fuel containing a biomass having a bulk density different from that of coal, having a high heat value at the same time, and having excellent handling properties can be provided.

Drawings

Fig. 1 is a flowchart of a fuel molding according to an embodiment.

FIG. 2 is a schematic view of an apparatus for measuring the strength of a formed fuel.

Fig. 3 is a flow chart of a shaped fuel according to another embodiment.

Fig. 4 is a graph showing the relationship between the half-carbonization temperature of biomass and the calorific value of biomass half-carbide.

Fig. 5 is a graph showing the evaluation results of the Hardgrove Grindability Index (HGI) of biomass semi-carbides.

Fig. 6 is a graph showing the change in compressive strength caused by the addition amount of polyvinyl alcohol.

FIG. 7 is a graph showing the results of measurement of the heat generation amount by oxidation of the mixture and coal.

FIG. 8 is a graph showing the results of measurement of the heat generation amount by oxidation of carbonized coal, biomass semi-carbide and coal.

Fig. 9 is a view showing a 2-stage combustion type test apparatus used in the experimental example.

FIG. 10 is a graph showing the relationship between the unburned components and the NOx concentration when the solid fuels of examples 2 to 5 and the bituminous coal of reference example 2 were combusted.

Fig. 11 is a graph showing the results of the evaluation 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.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. However, the following embodiments are examples for illustrating the present invention, and the present invention is not intended to be limited to the following.

[ shaped Fuel and Process for producing the same ]

Fig. 1 is a flowchart of a method for producing a molded fuel according to the present embodiment. The method for producing a molded fuel according to the present embodiment includes: a coarse pulverization step S1 for coarsely pulverizing the biomass; a drying step S2 for drying the biomass; a crushing step S3 of crushing coal containing at least one of lignite and subbituminous coal; a drying step S4 of drying the crushed coal; a carbonization step S5 of carbonizing the dried coal to obtain carbonized coal; a semi-carbonization step S6 of mixing the carbonized coal and the biomass and semi-carbonizing the biomass by sensible heat of the carbonized coal to obtain a mixture of a biomass semi-carbide and the carbonized coal; a pulverization step S7 for pulverizing the mixture; and a molding step S8 for molding the pulverized product to obtain a molded fuel.

In the present embodiment, biomass and coal containing at least one of lignite and subbituminous coal are used as the raw material. Biomass refers to a biologically derived resource other than fossil fuels. Examples of biomass include cut wood, pruned branches, waste wood, bark pieces, other woods, bamboo, grass, coconut shells, palm oil residues, vegetables, fruits, food residues, sludge, and the like. Among these biomass, woody biomass such as thinning, pruning, waste wood, bark pieces, and other woods is preferable. From the viewpoint of effective utilization of resources, the coal may be low-quality coal such as subbituminous coal and lignite. Even when low-quality coal is used, the surface area of the coal is reduced to suppress spontaneous combustibility as a molding fuel.

In the coarse grinding step S1, the biomass is cut and crushed. The size of the crushed pieces is not particularly limited, and the average value of the particle sizes is preferably more than 7mm, more preferably 10mm or more, from the viewpoint of improving the handleability in the subsequent step. On the other hand, from the viewpoint of sufficiently performing the semi-carbonization in the semi-carbonization step described later, the average value of the particle size is preferably less than 50mm, more preferably less than 40 mm. The average value of the particle size is a particle size at which the cumulative weight ratio when the pieces of biomass are sieved to obtain a particle size distribution reaches 50%. Bulk density example of BiomassFor example, it can be 0.1 to 0.6g/cm³. The water content of the biomass may be, for example, 10 to 60 mass%, or 30 to 60 mass%.

In the drying step S2, the biomass is dried in air at a temperature ranging from 20 to 150 ℃, for example. The drying step S2 may be performed in an inert gas atmosphere. Alternatively, the reaction may be carried out in the exhaust gas of a combustion furnace. In the drying step S2, the moisture content of the biomass is reduced to, for example, 0 to 30 mass%. By performing the drying step, the semi-carbonization of the biomass in the semi-carbonization step described later can be smoothly performed.

The drying step S2 may be performed using a normal 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 may be adjusted according to the moisture content, size, and the like of the biomass.

In the crushing step S3, the coal is crushed. The size of the crushed coal is not particularly limited, and the average particle size of the coal is preferably less than 50mm, more preferably less than 30mm, and still more preferably less than 10mm, from the viewpoint of smoothly proceeding the carbonization. The average value of the particle size is a particle size at which the cumulative weight ratio when the pieces of coal are sieved to obtain a particle size distribution reaches 50%. The moisture content of the coal is, for example, 30 to 60 mass%. The following drying step S4 is performed depending on the moisture content of the coal.

In the drying step S4, the coal is heated in air to a temperature in the range of, for example, 40 to 150 ℃. The drying step S4 may be performed in an inert gas atmosphere. Alternatively, the reaction may be carried out in the exhaust gas of a combustion furnace. In the drying step S4, the moisture content of the coal is reduced to, for example, 10 to 20 mass%. By performing the drying step S4, the heat load of the dry distillation step can be reduced, the dry distillation equipment can be made smaller, and the equipment cost can be reduced.

The drying step S4 may be performed using a normal 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 may be adjusted according to the moisture content, size, and the like of the coal.

The carbonization step S5 is a step of carbonizing the coal dried in the drying step S4 to obtain carbonized coal. The dry distillation step S5 may be performed without performing the drying step S4. At this time, the moisture content of the coal decreases in the initial stage of the dry distillation step S5. In the carbonization step S5, carbonized coal having a temperature of, for example, 400 to 800 ℃, preferably 450 to 650 ℃ is obtained. By setting the carbonized coal in this temperature range, the coal can be sufficiently modified and the biomass can be sufficiently semi-carbonized. The carbonization step S5 can be performed using a general carbonization furnace such as a vertical blast furnace, a coke oven, or a tunnel kiln.

The properties of coal change due to carbonization will be described below by taking brown coal as an example. Table 1 shows an example of properties of the carbonized coal obtained by heating brown coal at each temperature of 400 to 800 ℃ 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 carbonized coal obtained by carbonization at various temperatures. As shown in Table 1, the amount of carbon in the coal increased with the increase in the carbonization temperature and the removal of volatile components, and the calorific value increased. The same tendency is true for not only lignite but also subbituminous coal.

[ Table 1]

The average particle size of the carbonized coal is preferably less than 50mm, more preferably less than 30mm, further preferably less than 10 mm. The average value of the particle size is a particle size at which the cumulative weight ratio of the crushed pieces of the carbonized coal obtained by sieving the crushed pieces of the carbonized coal to obtain a particle size distribution reaches 50%.

In the semi-carbonization step S6, carbonized coal at a temperature in the range of 400 to 800 ℃ is mixed with biomass at normal temperature (for example, 40 ℃ or lower), and the biomass is semi-carbonized by the sensible heat of the carbonized coal to obtain a mixture containing biomass semi-carbides and carbonized coal. When the biomass is mixed with the carbonized coal heated in the carbonization step S5, the mixture is heated from room temperature to a temperature of 200 to 450 ℃ (half carbonization temperature) to become biomass half carbide. The term "semi-carbonization" in the present invention means a state in which a part of biomass is carbonized by carbonization treatment, but the biomass is not completely carbonized and still has room for carbonization. The semi-carbonization step S6 may be performed in a state where contact with air is substantially or completely blocked. As the equipment, for example, a vertical blast furnace, a kiln furnace, or the like can be used. By not completely carbonizing biomass and allowing the biomass to remain in a semi-carbonized state, the yield of biomass semi-carbides (carbonized products) can be sufficiently ensured, and the heat originally possessed by the biomass can be sufficiently utilized.

The half-carbonization temperature at the time of half-carbonizing biomass is preferably a temperature exceeding 200 ℃, more preferably 250 ℃ or higher, and further preferably 280 ℃ or higher, from the viewpoint of good pulverizability. On the other hand, the half-carbonization temperature is preferably 400 ℃ or lower, and more preferably 350 ℃ or lower, from the viewpoint of effectively utilizing the heat of the biomass.

The carbonized coal and the biomass may be mixed so that the molded fuel has a calorific value at a higher rank of 6000[ kcal/kg-dry ] or more, or may be mixed so that the calorific value at a higher rank of 6200[ kcal/kg-dry ] or more. For example, the biomass may be mixed in a proportion of 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 carbonized coal and the biomass. Thus, a molded fuel having both a high calorific value and excellent combustibility can be obtained at a high level. The temperature of the carbonized coal mixed with the biomass may be adjusted according to the mass ratio. Combustible gas and tar components generated in biomass semi-carbonization can also be recovered as fuel. This fuel can be used as a fuel in the dry distillation step S5, for example. In addition, the surplus heat can be recovered in the form of vapor and effectively utilized.

By semi-carbonizing biomass, the calorific value can be increased. The calorific value (higher calorific value) of the biomass semi-carbide may be 5000[ kcal/kg-dry ] or more, or 5,500[ kcal/kg-dry ] or more, for example. The amount of high-order heat generation of the biomass half-carbonized product based on the biomass before half-carbonization can be, for example, 1.1 times or more, preferably 1.2 times or more. By using the biomass semi-carbide, a formed fuel having a high calorific value can be produced.

In the grinding step S7, the mixture containing the carbonized coal and the biomass semi-carbide is ground. The particle size after pulverization is preferably less than 10mm, more preferably less than 5mm, from the viewpoint of good moldability. Biomass semi-carbides are superior in pulverizability to biomass before semi-carbonization. Therefore, the time and energy required for pulverization can be reduced as compared with the case of pulverizing the biomass before the semi-carbonization. Therefore, the molded fuel can be efficiently produced.

The biomass semi-carbide has a bulk density of, for example, 0.1 to 0.5g/cm³. The volume density of the carbonized coal may be, for example, 0.3 to 0.9g/cm³. If the carbonized coal and the biomass semi-carbide having different bulk densities are directly conveyed in a mixture state without being molded and are put into a combustion facility, they are easily separated due to the difference in bulk density, and the calorific value is easily changed. In the production method of the present embodiment, the following shaping step is performed, whereby separation of the carbonized coal and the biomass semi-carbide can be suppressed, and fluctuation in calorific value can be suppressed.

In the molding step S8, the molding material obtained by pulverizing the mixture in the pulverizing step S7 is molded to obtain a molded fuel. Examples of the apparatus for molding the molding material include a general twin-roll molding machine and a single-screw press molding machine. The shape of the molded fuel obtained by molding the molding material is not particularly limited, and may be, for example, a mosaic type, a spherical shape, a cylindrical shape, an almond shape, or a prismatic shape. From the viewpoint of improving handling properties, the average particle size of the molded fuel is preferably 5mm or more, and more preferably 10mm or more. The average value of the particle size is a particle size at which the cumulative weight ratio of the particle size distribution obtained by sieving the molded fuel reaches 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 tons/cm in terms of linear pressure and 20 to 390MPa in terms of surface pressure gauge.

In order to improve the moldability and the strength of the molded fuel, a binder may be added to a mixture (pulverized product) of the carbonized coal and the biomass semi-carbide to prepare a molding raw material. As the binder, for example, polyvinyl alcohol can be used. Thus, a molded fuel having excellent strength and water resistance can be produced.

In the above-described production method, the biomass is semi-carbonized by utilizing the sensible heat of the carbonized coal in the semi-carbonization step S6, and therefore, the energy loss can be reduced, and the molded fuel having a high calorific value can be efficiently produced. Further, since the dry distillation step S5 is performed, the calorific value of the shaped fuel can be increased as compared with the case where coal is directly used.

In addition, the above-described production method produces a shaped fuel by the shaping step S8 of shaping a shaping raw material obtained by pulverizing a mixture containing carbonized coal and biomass semi-carbides. The production method having the forming step S8 is superior in handling property to a method in which only biomass or biomass semi-carbide is mixed with coal or carbonized coal and burned, and a method in which these are fed into a combustion facility separately.

The strength of the formed fuel can be quantified by the compressive strength measured using the measuring apparatus 10 shown in fig. 2. As a sample, a cylindrical shaped fuel 16 (diameter 15 mm. times. height 15mm) was prepared. On the support plate 17 disposed on the bottom plate of the mount 18, the shaped fuel 16 is disposed such that the peripheral surface of the shaped fuel 16 to be measured is in contact with the upper surface of the support plate 17. Then, the movable plate 14, which is attached to the mount 18 so as to be movable up and down, is lowered, and the molded 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 shaped fuel 16. Finally, the compressive strength is determined from the load at the time of failure of the formed fuel 16.

When the aqueous polyvinyl alcohol solution is used as the aqueous binder solution in the molding step S8, a drying step of drying the molded product with, for example, an electric furnace or a dryer to reduce moisture may be performed after the molding step S8. The molded fuel may also be obtained by drying the molded product. The drying may be performed, for example, in air at 60 to 100 ℃ or in an inert gas atmosphere for 30 minutes to 20 hours. Alternatively, the reaction may be carried out in the exhaust gas of a combustion furnace. The drying reduces the moisture content of the formed fuel to preferably 5 mass% or less. By setting the water content to this amount, hydrogen bonding between polyvinyl alcohol molecules (between hydroxyl groups) can be sufficiently promoted, and the strength of the molded fuel can be further improved. The moisture content of the molded 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 compression strength of the formed fuel after the drying step is preferably 100N or more, more preferably 150N or more. The compression strength of the shaped fuel after 24 hours of immersion in water at 20 ℃ is preferably 40N or more, more preferably 50N or more. As can be seen, the molded fuel according to the present embodiment can maintain high strength even when wetted with water, not only when dried, by using, for example, polyvinyl alcohol as a binder.

The polyvinyl alcohol used as the binder in the forming step S8 may be an aqueous solution of polyvinyl alcohol (PVA) having a saponification degree of 99 mol% or more, preferably 99.3 mol% or more, more preferably more than 99.3 mol%, and still more preferably more than 99.8 mol%. The saponification degree represents the proportion of the unit actually saponified to a vinyl alcohol unit among the units convertible to the vinyl alcohol unit by saponification. The degree of saponification can be measured by a neutralization titration method based on JIS K6726-1994. Specifically, a phenolphthalein solution was added to polyvinyl alcohol, and sodium hydroxide was added dropwise until it became pale red. The residue (residual acetoxy group) was determined from the amount of the residue added dropwise, and the degree of saponification was calculated.

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

When polyvinyl alcohol having a saponification degree of 99 mol% or more is dried, hydroxyl groups of the respective molecules are strongly bonded by hydrogen bonds. Once formed, the bond does not readily dissociate even if contacted again with water. Therefore, a molded fuel obtained by molding with a binder containing an aqueous solution of polyvinyl alcohol having a saponification degree of 99 mol% or more is excellent in water resistance. From the viewpoint of further improving the strength of the molded fuel, the saponification degree of the polyvinyl alcohol is preferably 99.3 mol% or more, more preferably more than 99.3 mol%, and still more preferably more than 99.8 mol%.

Commercially available polyvinyl alcohols can be used. The polymerization degree of the polyvinyl alcohol is preferably 1700 or more, more preferably 2500 or more, and further preferably 3300 or more, from the viewpoint of improving the strength of the molded fuel particularly at the time of drying. The degree of polymerization of polyvinyl alcohol can be measured by solution viscometry based on JIS K6726-1994.

The content of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is preferably 1 to 10% by mass, more preferably 2 to 10% by mass. This facilitates kneading with a powdery molding material, and can improve dispersibility. Therefore, the uniformity of the molding material can be improved, and the strength variation of the molded fuel can be reduced.

The aqueous binder solution is excellent in safety as compared with a binder composed of only combustible substances. Further, since the molding material and the binder can be kneaded at room temperature without heating, even a carbonized coal having spontaneous combustibility can be kneaded with safety. However, kneading by heating is not excluded.

The molding raw material can be prepared by mixing and kneading a mixture of the carbonized coal and the biomass semi-carbide with an aqueous solution of polyvinyl alcohol. Water may be added and kneaded together depending on the viscosity of the aqueous polyvinyl alcohol solution or the content of polyvinyl alcohol in the aqueous solution. From the viewpoint of achieving both moldability and kneading property at a sufficiently high level, the proportion of the polyvinyl alcohol aqueous solution to 100 parts by mass of the powdery mixture may be, for example, 5 to 50 parts by mass or 5 to 30 parts by mass.

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

The binder may contain ingredients other than polyvinyl alcohol and water. The component may be a water-soluble component. As the water-soluble component, α starch is preferable from the viewpoint of production cost. Since alpha starch is generally cheaper than polyvinyl alcohol, the production cost of the molded fuel can be reduced by replacing a part of polyvinyl alcohol with alpha starch. In addition, when alpha starch is used, the strength of the molded fuel during drying can be sufficiently improved. In the molding fuel, the amount of the α starch is preferably 1 to 9 parts by mass per 100 parts by mass of the mixture, from the viewpoint of sufficiently improving the strength during drying while maintaining the water resistance.

In the modification of the above embodiment, an oxidation treatment step of oxidizing a mixture containing carbonized coal and biomass semi-carbides at a temperature range of, for example, 140 ℃ to 240 ℃ inclusive, preferably 160 ℃ to 200 ℃ inclusive, is provided between the semi-carbonization step S6 and the molding step S8. The oxidation treatment step may be performed before the pulverization step S7, or may be performed after the pulverization step S7. When the oxidation treatment is performed in this temperature range, the functional groups present on the surface of the carbonized coal are oxidized, and the oxygen content increases. Thus, the surface components of the carbonized coal are oxidized to stabilize the surface state, and thus the self-heat property is reduced and the self-heat property is suppressed. Further, oxidative decomposition accompanying the oxidation treatment is suppressed, and the yield of the molded fuel can be improved.

In the oxidation treatment step, the time for oxidizing the raw material coal in the temperature range is preferably 60 minutes or less. This can sufficiently improve the yield of the molded fuel.

The atmosphere in the oxidation treatment step is not particularly limited as long as it is an atmosphere containing oxygen, and may be air or a mixed atmosphere of an inert gas such as nitrogen and oxygen. Further, the exhaust gas may be an exhaust gas from a combustion furnace. The oxygen concentration may be, for example, 2 to 13 vol%, or 3 to 10 vol%, from the viewpoint of safety and efficiency of the oxidation treatment. The "volume%" is a 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 raw material coal are oxidized. This makes it possible to produce a molded fuel in which the self-heat property due to oxidation is reduced and the self-ignition property is sufficiently suppressed. From the viewpoint of improving the usefulness as a fuel, the volatile component (VM) of the molded fuel may be 5 mass% or more, or may be 10 mass% or more. On the other hand, from the viewpoint of further reducing the spontaneous combustibility, the volatile component (VM) of the molded fuel may be 30 mass% or less, or may be 25 mass% or less. In the present specification, the volatile component is a volatile component based on JIS M8812: value of dry basis measured by "Square electric furnace method" of 2006.

Fig. 3 is a method for producing a shaped fuel according to another embodiment. The manufacturing method comprises: a coarse pulverization step S1 for coarsely pulverizing the biomass; a drying step S2 for drying the biomass; a crushing step S3 for crushing coal; a drying step S4 of drying the coal; a carbonization step S5 of carbonizing the coal to obtain carbonized coal; a semi-carbonization step S6' for semi-carbonizing biomass to obtain a biomass semi-carbide; a pulverization step S7' for pulverizing the biomass semi-carbide; and a molding step S8 in which a mixture of the carbonized coal and the biomass semi-carbide is molded to obtain a molded fuel. The rough grinding step S1, the drying step S2, the crushing step S3, the drying step S4, the dry distillation step S5, and the forming step S8 may be performed in the same manner as in the above embodiment. Therefore, the description of the above embodiments can be applied.

In the semi-carbonization step S6', the biomass may be semi-carbonized using another heat source than the sensible heat of the carbonized coal. In addition, sensible heat of the carbonized coal may be used as a part of the heat source. The biomass semi-carbide can be obtained by heating biomass to a temperature (semi-carbonization temperature) of 200-450 ℃. Similarly to the semi-carbonization step S6, the semi-carbonization step S6' may be performed in a state in which the contact with air is substantially or completely blocked. As the equipment, for example, a vertical blast furnace, a kiln furnace, or the like can be used. In the modification, partial carbonization of the biomass may be performed by utilizing sensible heat of the carbonized coal, and the remaining biomass may be subjected to carbonization by using another heat source. Thereby allowing flexible operation.

In the pulverization step S7', the biomass semi-carbide is pulverized. The particle size after pulverization is preferably less than 10mm, more preferably less than 5mm, from the viewpoint of good moldability. Biomass semi-carbides are superior in pulverizability to biomass before semi-carbonization. Therefore, the time and energy required for pulverization can be reduced as compared with the case of pulverizing the biomass before the semi-carbonization. Therefore, the molded fuel can be efficiently produced.

In the forming step S8, the biomass half carbide may be mixed in an amount of 1 to 80 parts by mass, or 10 to 70 parts by mass, based on 100 parts by mass of the sum of the carbonized coal and the biomass half carbide. Thus, a molded fuel having both a high calorific value and excellent combustibility can be obtained at a high level.

In a modification of the above embodiment, an oxidation treatment step of subjecting a mixture obtained by mixing the carbonized coal and the biomass semi-carbide to oxidation treatment at a temperature range of, for example, 140 ℃ to 240 ℃ inclusive, preferably 160 ℃ to 200 ℃ inclusive, may be performed before the forming step S8.

The oxidation treatment step may be performed between the semi-carbonization step S6 'and the pulverization step S7', or the carbonized coal and the carbonized coal may be subjected to oxidation treatment before the carbonized coal and the carbonized biomass semi-carbide are mixed. In the oxidation step, the time for performing the oxidation treatment in the temperature range is preferably 60 minutes or less. This can sufficiently improve the yield of the molded fuel.

When the biomass semi-carbide and the carbonized coal are separately subjected to the oxidation treatment before being mixed, the oxidation treatment of the carbonized coal may be performed at 160 ℃ or more and 240 ℃ or less or 160 ℃ or more and 220 ℃ or less. The oxidation treatment of the biomass half-carbide may be performed at 100 ℃ or more and less than 200 ℃ or 130 ℃ or more and 180 ℃ or less. The safety can be sufficiently improved even when the biomass semi-carbide is subjected to the oxidation treatment at a temperature lower than that of the carbonized coal.

In the production method of each of the above embodiments, low-quality coal such as brown coal and sub-bituminous coal and biomass are used as raw materials, and CO having a calorific value equal to or higher than that of power coal for coal thermal power generation and produced by mixing biomass can be produced at low cost₂A molded fuel having a small discharge amount.

An embodiment of the molded fuel according to the present invention can be produced by, for example, the production methods of the above-described embodiments or their modifications. Therefore, the above description about the manufacturing method is also applicable to the formed fuel. The briquette fuel may contain pulverized coal of a mixture of coal-carbonized coal and biomass semi-carbide. The formed fuel is excellent in handling properties. The coal may comprise at least one of lignite and subbituminous coal. This can sufficiently increase the heat of the molded fuel. The content ratio of the carbonized coal and the biomass semi-carbide may be a ratio of the calorific value of the shaped fuel to 6000[ kcal/kg-dry ] or more on a dry basis, or a ratio of 6200[ kcal/kg-dry ] or more on a dry basis.

The shaped fuel may be obtained by shaping a raw material for shaping containing the pulverized product and the 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 the polyvinyl alcohol, the compressive strength of the molded fuel can be sufficiently improved and the water resistance can be improved.

The compression strength of the dried shaped fuel is preferably 100N or more, and more preferably 150N or more. The compression strength of the shaped fuel after 24 hours of immersion in water at 20 ℃ is preferably 40N or more, more preferably 50N or more. Here, the compressive strength 50N is a strength at which the molded fuel at the lowermost portion does not break even when it is loaded by its own weight in open air stacking at a stacking height of 15m, and is a strength at which pulverization during transportation can be suppressed.

The formed fuel according to one embodiment uses low-quality coal such as brown coal and subbituminous coal and biomass as raw materials, has a calorific value equal to or more than that of power coal for coal thermal power generation, and can reduce CO by mixing biomass₂And discharging the amount.

When the shaped fuel is immersed in 13 times by mass of water at 25 ℃ for 2 days, the COD of the water may be 500 ppm by mass or less, 400 ppm by mass or less, or 300 ppm by mass or less. This can sufficiently reduce the influence on the environment when, for example, the stack is placed in the open air. From the same viewpoint, when immersed in water under the same conditions, the turbidity of the water may be 200 degrees or less, or may be 100 degrees or less. From the same viewpoint, when immersed in water under the same conditions, the oil content in water may be 1wt ppm or less.

The formed fuel contains the carbonized coal, and therefore has a high calorific value. In addition, since biomass semi-carbide is contained, it has a small fuel ratio (fuel ratio ═ Fixed Carbon (FC)/volatile component (VM)). When the fuel ratio is small, the volatile component is high and therefore rich in ignitability, and the volatile component disappears immediately after the start of combustion, whereby the formed fuel becomes porous and the specific surface area becomes large. Therefore, the formed fuel is also excellent in combustibility. Further, the amount of harmful substances such as unburned components and nitrogen oxides generated can be reduced. The shaped fuel may be processed to any size for use as a solid fuel. Alternatively, other particulate matter may be mixed with the shaped fuel to produce a solid fuel.

The content of the biomass semi-carbide in the formed 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 sum of the carbonized coal and the biomass semi-carbide. This makes it possible to achieve both high heat generation and excellent combustibility at a high level.

While the present invention has been described with reference to the embodiments, the present invention is not limited to the embodiments. For example, in the process for producing the shaped fuel, the coarse pulverization step S1 and the pulverization step S3 may not be performed depending on the sizes of the biomass and the coal. Further, the drying step S2 or S4 may be omitted, and the drying step S5 or the semi-carbonization step S6 or S6' may be performed.

Examples

The present invention will be described in more detail with reference to the experimental results.

(preliminary experiments)

[ Change of Biomass due to semi-carbonization ]

As a biomass, pieces of eucalyptus (particle size: 10 to 50mm) were prepared. And heating the biomass for 2 hours at the temperature of 200-400 ℃ in an oxygen-free atmosphere by using an electric furnace to obtain the biomass semi-carbide. The biomass before the semi-carbonization and the biomass semi-carbides obtained by the semi-carbonization at each semi-carbonization temperature were measured for industrial analysis, elemental analysis, and high calorific value. The results are shown in Table 2.

[ Table 2]

The dry basis calorific value (higher calorific value) of the biomass semi-carbide shown in table 2 is marked in fig. 4. 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, biomass half-carbide was measured in accordance with JIS M8801. The results are shown in FIG. 5. In fig. 5, the results of biomass before semi-carbonization are given by the label of the semi-carbonization temperature of 25 ℃. As shown in fig. 5, it was confirmed that the biomass semi-carbide was more easily pulverized than the biomass. The average coal has a Hardgrove Grindability Index (HGI) of 30 to 70 (the region between the 2 solid lines in FIG. 5). From these results, it was confirmed that when the carbonization temperature is 200 ℃ or higher, the biomass carbonized material can have pulverizability equal to or higher than that of coal.

(Experimental example 1)

The biomass semi-carbide (semi-carbonization temperature: 320 ℃) shown in Table 2 was mixed with dry-distilled coal obtained by subjecting coal to dry distillation at 480 ℃ for 60 minutes to obtain a mixture. The mixing ratio was 30 parts by mass of biomass semi-carbide and 70 parts by mass of carbonized coal, based on 100 parts by mass of the total of the biomass semi-carbide and the carbonized coal. The average grain size of the biomass semi-carbide and the dry distillation coal is 0.2 mm. The mixture was mixed with an aqueous solution (binder aqueous solution) containing commercially available polyvinyl alcohol (degree of saponification: 99.85 mol%, degree of polymerization: 1700) at a concentration of 10 mass% and water to obtain a molding material. The compounding ratio in this case is varied from 10 to 40 parts by mass (1 to 4 parts by mass of the binder) of the aqueous binder solution per 100 parts by mass of the mixture, thereby preparing a variety of molding materials.

Each molding material was molded (molding pressure: 283MPa) using a single-screw press molding machine to prepare a cylindrical (diameter: 15 mm. times. height: 15mm) molded fuel. The molded fuel thus produced was dried in air at 80 ℃ for 15 hours. The moisture content after drying was measured by a heat drying method using a commercially available moisture measuring machine, and was 2% by mass in all cases. The compressive strength of the dried formed fuel was measured by using the measuring apparatus shown in FIG. 2. The measurement results are shown in table 3 (after drying) and fig. 6 (black dots). The remarks in table 3 show the types of examples and comparative examples.

Each of the dried shaped fuels was immersed in water at about 20 ℃ for 24 hours. Then, the molded fuel was taken out from the water, and the compressive strength was measured using the measuring apparatus of FIG. 2. The measurement results are shown in table 3 (after water immersion) and fig. 6 (black triangles in fig. 6). It was confirmed that the strength after water immersion could be sufficiently improved by using polyvinyl alcohol as a binder, and a molded fuel having a strength exceeding the target strength (40N or more) even after water immersion could be produced.

[ Table 3]

As shown in fig. 6, it was confirmed that the compressive strength could be improved by increasing the blending ratio of polyvinyl alcohol.

(Experimental example 2)

The biomass semi-carbide (320 ℃ C.) in Table 2 was mixed with dry distilled coal obtained by subjecting coal to dry distillation at 480 ℃ for 60 minutes to obtain a mixture. The mixing ratio was 50 parts by mass of the biomass semi-carbide and 50 parts by mass of the carbonized coal, respectively, based on 100 parts by mass of the total of the biomass semi-carbide and the carbonized coal.

The mixture was heated at a temperature of 180 ℃ for 60 minutes under an atmosphere having an oxygen concentration of 5 vol%. This oxidation treatment step was performed to obtain a mixture (mixed fuel) (50 parts by mass of carbonized coal, biomass semi-carbide, 50 parts by mass). An oxidation heat amount measurement test (DSC test) of the prepared mixed fuel was performed. In this test, 10mg of a mixed fuel pulverized to 212 μm or less was charged into an alumina sample container, the temperature of the sample was raised to 107 ℃ under a nitrogen atmosphere, and after reaching 107 ℃, the atmosphere was switched to air, and the change with time of the heat generation temperature of the sample was examined. The results are shown in the graph of fig. 7 (solid line 1).

For comparison, the evaluation results (one-dot chain line 2) of the mixture not subjected to the oxidation treatment step and the evaluation results (sub-bituminous coal: dotted line 3, bituminous coal: two-dot chain line 4) of the coals (sub-bituminous coal and bituminous coal) are shown in fig. 7. As shown in fig. 7, it was confirmed that heat generation was difficult and safety was improved by performing oxidation treatment of the mixture.

DSC tests were performed on carbonized coal and biomass semi-carbides used as raw materials of a mixed fuel, oxidized products obtained by oxidizing the carbonized coal and the biomass semi-carbides, and coal (subbituminous coal and bituminous coal). The results are shown in FIG. 8. In fig. 8, a solid line 1 represents the carbonized coal after the oxidation treatment, and a solid line 2 represents the carbonized coal before the oxidation treatment. The two-dot chain line 3 indicates the biomass half-carbide after the oxidation treatment, and the one-dot chain line 4 indicates the biomass half-carbide before the oxidation treatment. Dashed line 5 represents sub-bituminous coal and dashed line 6 represents bituminous coal.

The oxidation treatment of biomass half-carbide was performed by heating at a temperature of 160 ℃ for 60 minutes in an atmosphere with an oxygen concentration of 5 vol%. The oxidation treatment of the carbonized coal was performed by heating at a temperature of 220 ℃ for 40 minutes in an atmosphere having an oxygen concentration of 5 vol%. From the results shown in FIG. 8, it was confirmed that the safety of the carbonized coal and biomass semi-carbide was improved by the oxidation treatment.

(Experimental example 3)

The biomass semi-carbides (semi-carbonization temperature: 320 ℃) in table 2 and the carbonized coal obtained by subjecting lignite to dry distillation at 480 ℃ for 60 minutes were mixed in such a ratio that the biomass semi-carbides are 1 to 80 parts by mass when the total of both is 100 parts by mass, to obtain various mixtures. Table 4 summarizes the industrial analysis, the elemental analysis, and the higher calorific value of the molded fuel obtained by molding each of these mixtures. Since the calorific value of the power coal used in coal-fired power generation is usually 6,000[ kcal/kg-dry ] or more, it was confirmed that the molded fuel obtained by molding a mixture of the carbonized coal and the biomass semi-carbide can also have the calorific value equivalent to that of the power coal.

The coal carbonization temperature, the biomass semi-carbonization temperature, and the mixing ratio in experimental examples 1 and 2 are examples. By adjusting these, a molded fuel having an arbitrary calorific value of, for example, 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 may be appropriately changed.

Table 4 shows the results of industrial analysis of the molded fuel and CO in thermal power generation using the molded fuel₂And discharging the amount. Conventionally, when coal and biomass in an amount of 3% in terms of calorific ratio were CO-fired without semi-carbonizing biomass, CO was used₂The discharge rate was 0.838kg-CO₂and/kWh. In contrast, as shown in table 4, by increasing the mixing ratio of the biomass semi-carbide in the formed fuel, CO can be greatly reduced₂And discharging the amount. When the mixing ratio of the biomass semi-carbide is increased, the Volatile Matter (VM) increases, and the combustibility improves.

[ Table 4]

(Experimental example 4)

This mixture was mixed with the aqueous binder solution used in experimental example 1 and water to obtain a molding material. The compounding ratio in this case was 30 parts by mass (3 parts by mass in terms of the binder) of the binder aqueous solution and 10 parts by mass of water per 100 parts by mass of the mixture. The molding material was molded by a two-roll molding machine to prepare an almond-shaped molded fuel (24 mm × 16mm × 13mm in length × height). The formed fuel thus produced was dried in air in sunlight for 5 hours. The forming pressure was 3 t/cm. The mass of the dried molded fuel was 135g, and the water content was about 7 mass% (example 1). In addition to the above molding materials, biomass semi-carbide (semi-carbonization temperature: about 300 ℃ C., calorific value: about 5000kcal/kg-dry) was prepared. The biomass half-carbide mass was 135g (reference example 1).

The shaped fuel of example 1 and the biomass semi-carbide of reference example 1 were immersed in water 13 times the mass of each, and left to stand at 25 ℃ for 48 hours. After standing, the solid component was removed from the water using a sieve having a mesh opening of 0.5 mm. The thus obtained water (dissolved-out water) was measured for oil content, Chemical Oxygen Demand (COD), and turbidity. The oil content was measured as the amount of n-hexane extracted substance. The turbidity was measured according to JIS K0101 "Industrial Water test method". The measurement method was carried out by the transmitted light method, and kaolin was used as a turbidity standard solution. Chemical Oxygen Demand (COD) by acidic high-temperature permanganic acid method using potassium permanganate_Mn) To be measured. The results are shown in Table 5. In table 5, the analysis value of water before the molding material was immersed is shown as a blank.

[ Table 5]

The turbidity and COD of the formed fuel in example 1 were about 10% of the biomass half-carbide in reference example 1. It was confirmed that the molded fuel of example 1 can sufficiently reduce the influence on the environment as compared with reference example 1 even when stored in a stacked state in the open air, for example.

(Experimental example 5)

[ use of Molding Fuel ]

< example 2 >

The biomass semi-carbide (320 ℃) in Table 2 and the carbonized coal obtained by distilling coal at 480 ℃ for 60 minutes were subjected to oxidation treatment. The oxidation treatment of biomass half-carbide was performed by heating at a temperature of 160 ℃ for 60 minutes in an atmosphere with an oxygen concentration of 5 vol%. The oxidation treatment of the carbonized coal was performed by heating at a temperature of 220 ℃ for 40 minutes in an atmosphere having an oxygen concentration of 5 vol%.

And mixing the biomass semi-carbide subjected to the oxidation treatment with the dry distillation coal subjected to the oxidation treatment to obtain a mixture. The mixing ratio was 50 parts by mass of the biomass semi-carbide and 50 parts by mass of the carbonized coal, respectively, based on 100 parts by mass of the total of the biomass semi-carbide and the carbonized coal. The mixture was mixed with the aqueous binder solution used in experimental example 1 and water to obtain a molding material. The compounding ratio in this case was 35 parts by mass (3.5 parts by mass in terms of the binder) of the binder aqueous solution and 5.5 parts by mass of water, relative to 100 parts by mass of the mixture.

The molding material was molded by a two-roll molding machine to prepare an almond-shaped molded fuel (24 mm × 16mm × 13mm in length × height). The formed fuel thus produced was dried in air in sunlight for 5 hours. The forming pressure was 3 t/cm. Crushing the formed fuel by a mill to obtain a crushed material with the particle size of 1-220 mu m. The crushed material was mixed with bituminous coal to prepare a solid fuel for testing. The mass ratio of the shaped fuel fragments in the solid fuel was 30%. This was used as the solid fuel of example 2.

< example 3 >

A solid fuel for a test was produced in the same manner as in example 2, except that the mixing ratio of the oxidized biomass semi-carbide and the oxidized carbonized coal was changed to 30 parts by mass and 70 parts by mass, respectively, based on 100 parts by mass of the total of the oxidized biomass semi-carbide and the carbonized coal. This was used as the solid fuel of example 3.

< example 4 >

In addition to the pieces of eucalyptus used in the preliminary experiment, pieces of pine trees and construction waste wood were prepared. With pieces of eucalyptus: pine tree debris: building waste wood 7: 7: 6 to prepare the biomass. The biomass is heated for 2 hours at 320 ℃ in an oxygen-free atmosphere to obtain biomass semi-carbide. A solid fuel was produced in the same manner as in example 2, except that this biomass half carbide was used.

< example 5 >

Biomass semi-carbides were obtained in the same order as in example 4. A solid fuel was produced in the same manner as in example 3, except that this biomass semi-carbide was used.

< reference example 2 >

Bituminous coal (Wanmu coal) was prepared. This was pulverized by a mill to obtain a solid fuel according to reference example 2.

[ burning test ]

The solid fuels of examples 2 to 5 and the bituminous coal of reference example 2 were supplied to a 2-stage combustion test apparatus shown in fig. 9, respectively, and a combustion test was performed. The solid fuel is supplied from the inlet 30a to the burner 30 of the test apparatus, and the primary air is supplied from the air supply pipe 31. Further, secondary air is supplied from the air supply pipe 32 to the main body 40 of the combustion apparatus. The supply ratio of primary air and secondary air was 7: 3. The main body 40 of the combustion apparatus is provided with 5 secondary air supply ports (

supply ports

41, 42, 43, 44, 45).

Combustion tests were conducted using the

supply ports

41, 42, 43, 44, and 45 alone, and the unburned components and NOx concentrations of the combustion exhaust gas discharged from the exhaust port 48 were measured. The measurement results of the concentrations of unburned components and nitrogen oxides (NOx) when the supply ports were used are shown in tables 6 and 7, respectively. The unburned components and NOx were measured by thermogravimetric analysis and infrared absorption.

[ Table 6]

[ Table 7]

As shown in table 6, in examples 2 to 5, the unburned components were reduced as compared with the case of using the bituminous coal. Fig. 10 is a graph showing the relationship between the unburned components and the NOx concentration. Curve 1 represents the results of reference example 2, curve 2 represents the results of example 2, curve 3 represents the results of example 3, curve 4 represents the results of example 4, and curve 5 represents the results of example 5. From the results of fig. 10, it was confirmed that the amount of NOx generated was also reduced in examples 2 to 5 (curves 2 to 5) as compared with reference example 2 (curve 1) if the same unburned components were compared.

[ evaluation of Natural Heat Generation ]

The natural exothermic properties of the solid fuels of examples 2 to 5 and the bituminous coal of reference example 2 were evaluated by an adiabatic type measurement method (method R70) for evaluating the natural exothermic properties of coal at 40 to 70 ℃. Specifically, 200g of the sample was charged into a reaction vessel, and the reaction vessel was placed in a thermostatic bath at 40 ℃. The reaction container is connected to a gas supply unit for supplying air at the same temperature as the temperature of the sample in the reaction container. The temperature rise curve of the sample in the reaction vessel was measured.

FIG. 11 is a graph showing temperature rise curves of the solid fuels of examples 2 to 5 and the bituminous coal of reference example 2 according to the R70 method. Curve 1 represents the results of reference example 2, curve 2 represents the structure of example 2, curve 3 represents the results of example 3, curve 4 represents the results of example 4, and curve 5 represents the results of example 5. As shown in fig. 11, it was confirmed that the solid fuels of examples 2 to 5 were superior in safety because the natural heat generation was suppressed as compared with the bituminous coal of reference example 2.

Description of the reference numerals

10 … measurement device, 14 … movable plate, 16 … molded fuel, 17 … support plate, 18 … mount, 30 … burner, 31, 32 … air supply pipe, 40 … main body part, 41, 42, 43, 44, 45 … supply port, 48 … exhaust port.

Claims

1. A method for producing a molded fuel, comprising the steps of:

a carbonization step of carbonizing coal containing at least one of lignite and subbituminous coal to obtain carbonized coal; and the number of the first and second groups,

and a molding step of molding a mixture containing the carbonized coal and a biomass half-carbide obtained by half-carbonizing a biomass to obtain a molded fuel.

2. The method for producing a shaped fuel according to claim 1, comprising the steps of: a semi-carbonization step of semi-carbonizing the biomass to obtain a biomass semi-carbide; and a pulverization step of pulverizing the biomass semi-carbide,

mixing the pulverized biomass semi-carbide with the carbonized coal to obtain the mixture.

3. The method for producing a shaped fuel according to claim 1 or 2, comprising an oxidation treatment step of subjecting the carbonized coal and the biomass semi-carbide to oxidation treatment,

in the oxidation treatment step, the carbonized coal is heated to a temperature range of 160 ℃ to 240 ℃ inclusive, and the biomass semi-carbide is heated to a temperature range of 100 ℃ to less than 200 ℃.

4. The method for producing a shaped fuel according to claim 1, comprising a semi-carbonization step of semi-carbonizing the biomass by sensible heat of the carbonized coal to obtain the mixture.

5. The method for producing a shaped fuel according to claim 1 or 4, which comprises a pulverization step of pulverizing the mixture before the shaping step.

6. The method for producing a shaped fuel according to any one of claims 1, 4, and 5, wherein the biomass is semi-carbonized by heating to 200 to 450 ℃ by mixing with the carbonized coal at a temperature in the range of 400 to 800 ℃.

7. The method for producing a shaped fuel according to any one of claims 1, 2, and 4 to 6, which comprises an oxidation treatment step of subjecting the mixture to an oxidation treatment at a temperature range of 140 ℃ to 240 ℃.

8. The method for producing a shaped fuel according to any one of claims 1 to 7, comprising the following steps before the biomass is semi-carbonized:

a coarse pulverization step of coarsely pulverizing the biomass so that the average particle size of the biomass is greater than 7mm and less than 50 mm; and the number of the first and second groups,

and a drying step of drying the coarsely pulverized biomass.

9. The method for producing a molded fuel according to any one of claims 1 to 8, wherein a binder containing polyvinyl alcohol having a saponification degree of 99 mol% or more is used in the molding step.

10. The method for producing a molded fuel according to claim 9, wherein the degree of polymerization of the polyvinyl alcohol is 1700 or more.

11. The method for producing a shaped fuel according to any one of claims 1 to 10, wherein when the shaped fuel is immersed in water having a mass 13 times that of the shaped fuel at 25 ℃ for 2 days, the water has a COD of 500 ppm by mass or less.

12. A briquette fuel comprising a carbonized coal and a biomass semi-carbide, wherein the carbonized coal is a carbonized coal comprising coal of at least one of lignite and subbituminous coal.

13. The shaped fuel according to claim 12, which contains polyvinyl alcohol having a saponification degree of 99 mol% or more.

14. The shaped fuel according to claim 12 or 13, wherein the COD of water is 500 mass ppm or less when immersed in 13 times by mass of water at 25 ℃ for 2 days.