solid fuels

Abstract

The object of the present invention is to provide a solid fuel formed from crushed hardwood, which has a high material yield and calorific value yield, is easy to handle from the viewpoints of recycling and environmental protection, has improved transportability, and is excellent in mill pulverizability. The product is made of pellets containing crushed hardwood and has a bulk density of 600 to 680 kg / m 3 and has a mechanical durability of 95.0% or more, and when the pellets of the solid fuel are dry-crushed, the fraction that passes through a sieve with 1 mm square holes after dry-crushing is 60% by mass or more.

Description

[Technical Field]

[0001] The present invention relates to a technique for producing solid fuel from hardwood. [Background technology]

[0002] In recent years, the use of fuels made from biomass has been considered as a measure to combat the depletion of fossil fuels and global warming caused by CO2 emissions. Generally, biomass refers to living organisms that can be used as an energy source or industrial raw material, and typical examples include wood, construction waste, and agricultural waste.

[0003] One known technique for producing solid fuel using biomass as a raw material is to carbonize the biomass to produce solid fuel. This involves carbonizing the biomass in a carbonization furnace and heating it for a predetermined period of time in an oxygen-deficient atmosphere to produce solid fuel. The solid fuel produced in this way is used as fuel for combustion facilities such as power generation facilities and incineration facilities. In this case, the solid fuel may be finely pulverized and used as pulverized fuel to improve combustion efficiency.

[0004] Patent Document 1 discloses a method of pyrolyzing woody biomass such as waste lumber, thinned wood, garden trees, and construction waste at 240 to 300°C for 15 to 90 minutes, followed by pulverization. Patent Document 2 discloses a method of producing solid fuel with pulverizability equivalent to that of coal by carbonizing biomass including grains, fruits, and seeds by heating it at an oxygen concentration of 1 to 5% and a treatment temperature of 350 to 400°C for 30 to 90 minutes.

[0005] Furthermore, Patent Document 3 describes compressing and dehydrating wood chips for thermal utilization, and Patent Document 4 describes compressing and solidifying plant materials such as wood to produce solid fuel. Furthermore, Non-Patent Document 1 describes compressing and dehydrating bark using a reciprocating press and utilizing it for thermal utilization in a boiler or the like. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-026474 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-191085 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-036666 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-189457 [Non-patent literature]

[0007] [Non-Patent Document 1] International Journal Energy Engineering, 2014, volume 4, pages 8-16 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0008] Fuels obtained by carbonizing plant biomass such as wood generally have problems with low material yield and calorific yield. Furthermore, producing solid fuel using biomass such as wood as a raw material involves costs, such as transporting the biomass, which creates cost issues compared to coal. Therefore, efforts have been made to convert crushed wood into pellets or other solid fuels for ease of handling and transportation. However, the wood must be crushed in a mill before being fed into a boiler, which can sometimes result in problems with crushability. [Means for solving the problem]

[0009] The inventors have investigated solid fuels consisting of shaped products containing crushed hardwood that are easy to grind in a mill, and have found that by making the fraction of the shaped products containing crushed hardwood that pass through a sieve with 1 mm square holes after dry crushing 60 mass% or more of the solid fuel shaped products, which have a particle size of 60 mass% or more, a solid fuel that is easy to grind in a mill using hardwood as a raw material can be obtained, which has led to the completion of the present invention.

[0010] The present invention includes, but is not limited to, the following aspects. (1) A solid fuel consisting of a molded product containing crushed hardwood, in which the fraction of the molded product of the solid fuel that passes through a sieve with 1 mm square holes after dry crushing is 60 mass% or more. (2) The solid fuel according to (1), wherein the solid fuel is a pellet having an average length of 22 mm or less. (3) The bulk density of the crushed hardwood molding is 600 kg / m 3 More than 680kg / m 3 The solid fuel according to any one of (1) to (2) below: (4) The solid fuel according to any one of (1) to (3), having a mechanical durability of 95.0 to 97.0%. (5) The solid fuel according to any one of (1) to (4), wherein the size of the pulverized material is 50 mm or less and the moisture content is 8 to 30%. (6) The solid fuel according to any one of (1) to (5), wherein the solid fuel is a pellet formed from pulverized acacia chips with husks. (7) A solid fuel according to any one of (1) to (6), in which B / A, which is the ratio of the fraction A (%) passing through a sieve with 1 mm square holes measured after dry crushing to the fraction B (%) passing through a sieve with 1 mm square holes measured after wet crushing according to ISO17830:2016, is 0.8 to 1.2. (8) A method for producing the solid fuel according to any one of (1) to (7), comprising a step of molding the solid fuel from pulverized hardwood. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a solid fuel made from a molded product of pulverized hardwood, which has excellent mill-pulverizability. That is, according to the present invention, the molded product is easy to handle and improves transportability. Furthermore, according to the present invention, since a solid fuel can be produced from woody biomass as a raw material by a simple method, the material yield and calorific yield are high, and the present invention is extremely useful from the viewpoints of recycling and environmental protection. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention relates to a technology for producing solid fuel from biomass containing wood. In the present invention, biomass containing wood (hereinafter also referred to as woody biomass) is used as a raw material, but as long as it contains wood, it may also contain herbaceous plants, etc. Examples of wood include wood chips, bark, sawdust, forest residues, and construction waste, and a preferred example is wood chips as a raw material. In the present invention, the species of wood is not particularly limited, and both broadleaf and coniferous trees can be used, but coniferous trees are preferred. Furthermore, only one type of wood can be used, or multiple types can be mixed. In addition to wood, bark can also be used as a raw material in the present invention.

[0013] The broad-leaved trees used in the present invention are not particularly limited, but examples include acacia, eucalyptus, rubber tree, beech, Chinese linden, white birch, poplar, oak, sugar maple, Asiatic ash, elm, paulownia, magnolia, willow, ash, phillyraeoides phillyraeoides, oak, sawtooth oak, horse chestnut, zelkova, beech, dogwood, and ash tree.

[0014] In the present invention, it is preferable to use hardwood that has been crushed to a size of 50 mm or less before being made into a molded product, and it is preferable to use pulverized material with a size of 0.1 to 50 mm. In the present invention, the size of the crushed material refers to the size of the circular holes in a sieve. As an apparatus for crushing hardwood, it is preferable to use a knife-cutting type biomass fuel chipper.

[0015] The solid fuel used as a raw material in the present invention contains hardwood as described above, and the weight ratio of hardwood is, for example, preferably 50% by weight or more, and may be 70% by weight or more. In one embodiment, it is also possible to use only hardwood as a raw material.

[0016] In the present invention, the obtained pulverized hardwood is formed into briquettes or pellets, and the bulk density of the formed products (measured in accordance with JIS K 2151-6 "Bulk Density Test Method") is 600 kg / m 3 More than 680kg / m 3 is preferable, and 602 to 650 kg / m 3 More preferably, 604 to 620 kg / m 3 By forming the solid fuel into a molded product, it is possible to improve the handling properties of the solid fuel and reduce the transportation costs.

[0017] In one embodiment, the solid fuel formed product of the present invention, after dry crushing, must have a particle size of 60% by mass or more, more preferably 65 to 90% by mass, and even more preferably 70 to 80% by mass or more, that passes through a sieve with 1 mm square holes. The crushability of a solid fuel formed product is typically measured by crushing the formed product in hot water in accordance with ISO 17830:2016(E) Solid biofuels—Particle size distribution of disintegrated pellets. In contrast, the present invention involves dry crushing of the formed product, and it has been found that the method of the present invention has a better correlation with mill grindability. If the fraction passing through a sieve with 1 mm square holes is 60% by mass or more, the mill grindability is excellent.

[0018] The solid fuel according to the present invention has a ratio B / A of the fraction B (%) passing through a sieve with 1 mm square holes measured after dry crushing to the fraction A (%) passing through a sieve with 1 mm square holes measured after wet crushing according to ISO17830:2016, which is preferably 0.8 to 1.2, more preferably 0.85 to 1.15, and even more preferably 0.9 to 1.1. Here, the fraction passing through a sieve with 1 mm square holes is measured according to EN15149-2:2010.

[0019] The average length of the solid fuel moldings is preferably 21 mm or less, more preferably 10 to 20 mm, and even more preferably 15 to 19 mm. By setting the average length to 21 mm or less, excellent grindability in a mill is achieved. The diameter of the moldings is preferably in the range of 5 to 15 mm, more preferably 6 to 13 mm, and even more preferably 7 to 11 mm.

[0020] In the present invention, the molding device for molding the pulverized material is not particularly limited, but a briquette (manufactured by Kitagawa Iron Works), a ring die pelletizer (manufactured by CPM), a flat die pelletizer (manufactured by Dalton), etc. are desirable.

[0021] In the present invention, when pulverized hardwood material is molded into a molded product, the moisture content of the pulverized hardwood material is preferably 8 to 50%, more preferably 9 to 30%, and even more preferably 10 to 20%. If the moisture content is less than 8%, clogging occurs inside the briquette or pelletizer, making it impossible to produce a stable molded product. If the moisture content exceeds 50%, molding is difficult and the material is discharged in a powder or paste form.

[0022] The molded solid fuel of the present invention preferably has a mechanical durability (based on the Wood Pellet Quality Standard 6.5 Mechanical Durability Test Method) of 95% or more. Mechanical durability within this range means that the pellets are sufficiently hard to avoid being crushed and pulverized during transportation. Mechanical durability indicates the resistance of the pellets to breakage, and is the mass percentage of pellets that do not break and pulverize when subjected to a certain amount of mechanical impact. In a more preferred embodiment, the mechanical durability of the molded solid fuel of the present invention is 97% or more.

[0023] In the present invention, 1 to 50 parts by mass of binder may be added to 100 parts by mass of ground hardwood. There are no particular limitations on the binder, but organic polymers (such as lignin or starch), inorganic polymers (such as acrylic acid amide), agricultural residues (such as bran (residue generated during wheat flour production)), etc. are desirable. From the viewpoint of efficiently and effectively utilizing woody biomass, it is desirable to add as few binders as possible, 1 to 50 parts by mass, and more preferably 1 to 20 parts by mass. However, adding more than 50 parts by mass does not necessarily mean that high density is impossible.

[0024] The solid fuel obtained by the present invention is used as a fuel for boilers, and is particularly suitable as a fuel for coal boilers, since it can be mixed with coal and pulverized to be combusted with coal. [Example]

[0025] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Furthermore, in this specification, parts, % and the like are by weight, and numerical ranges are stated as including their endpoints.

[0026] [Example 1] Acacia chips with husks were pulverized using a disc chipper. After pulverization, the material passed through a 50 mm screen was used as raw material and dried in a dryer at 120°C for 20 minutes to adjust the moisture content to 10%. The moisture content of the resulting pulverized material was adjusted to 12% and densified using a ring die pelletizer (manufactured by CPM) with a flat die having a die hole diameter of 8 mm and an effective die hole length of 52 mm to obtain solid fuel pellets.

[0027] The resulting molded product was measured for the following items. Average length: Measured according to ISO17829:2015. Bulk density: Measured according to ISO17829:2015. Mechanical durability: Measured according to ISO17831:2015. Particle size after dry crushing (B): 20 g of dried extrudate was crushed for 12 seconds in a LabMill (Osaka Chemical Co., Ltd.), and the particle size was measured by measuring the percentage of the fraction that passed through a 1 mm square sieve in accordance with EN15149-2:2010 (Solid biofuels. Determination of particle size distribution. Vibrating screen method using sieve apertures of 3.15 mm and below). For the wet crushing described below, 2000 ml of water was added to a 300 g sample for crushing. Dry crushing was performed in accordance with ISO17830:2016(E), except that the dried extrudate was crushed without adding water. Particle size after wet crushing (A): The dried extruded material was wet crushed in accordance with ISO17830:2016(E) (Solid biofuels - Particle size distribution of disintegrated pellets), and the particle size was measured by measuring the percentage of the fraction that passed through a sieve with 1 mm square openings in accordance with EN15149-2:2010 (Solid biofuels. Determination of particle size distribution. Vibrating screen method using sieve apertures of 3.15 mm and below). Biomass mill input amount: The input amount of the molded material to the biomass mill was adjusted so that the mill differential pressure could be operated at 5.0 kPa in a dedicated biomass mill (manufactured by IHI).

[0028] [Example 2] to [Example 5] Examples 2 to 5 were produced under the same conditions as Example 1, except that the same acacia chips with husks were used but were delivered at different times.

[0029] [Comparative Example 1] to [Comparative Example 4] Comparative Examples 1 to 4 were made using the same acacia chips with skin, but at different times of arrival, and were produced under the same conditions as Example 1, except that the cutter position was adjusted to set the effective hole length of the ring die to 72 mm.

[0030] [Table 1]

[0031] As shown in Table 1, the extruded products of Examples 1 to 5 had good crushability in a biomass mill, and therefore the input amount to the biomass mill was high. On the other hand, as shown in Comparative Examples 1 to 4, even if the proportion of the fraction that passed through 1 mm square holes in the particle size measured after wet crushing was high, if the fraction that passed through 1 mm square holes in the particle size measured after dry crushing of the present invention was less than 60%, it was clear that the input amount to the biomass mill would decrease.

Claims

1. It is made of pellets containing crushed hardwood and has a bulk density of 600 to 680 kg / m ３ A solid fuel having a mechanical durability of 95.0% or more, A solid fuel in which, when pellets of the solid fuel are dry-crushed, the fraction of the particle size after dry-crushing that passes through a sieve with 1 mm square holes is 60 mass% or more.

2. 2. The solid fuel according to claim 1, wherein the solid fuel is in the form of pellets having a bulk density of 600 to 620 kg / m 3 and an average length of 22 mm or less.

3. A solid fuel as described in claim 1 or 2, wherein the dry crushing is dry crushing for 12 seconds using a LabMill (Osaka Chemical), and the fraction is 90 mass% or less.

4. 4. The solid fuel according to claim 1, wherein the mechanical durability is 95.0 to 97.0%.

5. 5. The solid fuel according to claim 1, wherein the size of the pulverized material is 50 mm or less and the moisture content is 8 to 30%.

6. 6. The solid fuel according to claim 1, wherein the solid fuel is a pellet formed from crushed acacia chips with husks.

7. 7. The solid fuel according to claim 1, wherein B / A is a ratio of a proportion B (%) of a fraction that passes through a sieve having 1 mm square holes measured after dry crushing to a proportion A (%) of a fraction that passes through a sieve having 1 mm square holes measured after wet crushing according to ISO 17830:2016, and is 0.8 to 1.2.

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