Wood chip and use thereof

Abstract

To provide a wood chip useful for various applications such as a fuel.SOLUTION: The present invention provides wood chips derived from eucalyptus plants such as hybrids of E. pelita and E. brassiana having a fiber length of 1. 10mm or less, a volume weight 635kg / m3 or more, and a maximum moisture regain of 40% or less. The wood chips preferably have a lower heating value of 1800kcal / kg or more at the maximum water content. The eucalyptus plant preferably has an age of 2 years or more and 15 years or less. The wood chips of the present invention can be used as a fuel for heat utilization, power generation, or heat and power supply.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to wood chips and uses thereof. [Background technology]

[0002] To prevent global warming and build a sustainable society, it is important to reduce greenhouse gas emissions, promote CO2 absorption and fixation, and promote the use of biomass, a recyclable resource. Switching to non-fossil fuels and promoting energy conservation are effective ways to reduce greenhouse gas emissions, and biomass fuels are expected to become increasingly important in the future due to the concept of carbon neutrality. Large-scale commercial afforestation is also an effective method for CO2 absorption and fixation and increasing biomass resource production. Commercial afforestation requires cost reduction, which requires increasing the yield (weight) of biomass per unit area. Wood chips obtained from commercial afforestation are transported by chip ships. Because chip ships have limited capacity, there is a demand for high-density chips that can carry larger amounts of chips in the same volume (reducing transportation costs).

[0003] Non-Patent Document 1 states that the volume density of a 7.5-year-old eucalyptus clone is 0.53 to 0.59 g / cm 3 It is stated that it was. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Pereira,B.et al(2012)International Journal of Forestry Research,Vol.2012,Article ID 523025,8 pages doi:10.1155 / 2012 / 523025https: / / downloads.hindawi.com / journals / ijfr / 2012 / 523025.pdf Summary of the Invention [Problem to be solved by the invention]

[0005] For fuel biomass, it is important not only to improve plantation yield (weight) and transportation efficiency, but also to improve fuel suitability. However, there have been no reports, including Non-Patent Document 1, on the relationship between the physical properties of wood and fuel suitability. An object of the present invention is to provide wood chips that are useful for various purposes, such as fuel. [Means for solving the problem]

[0006] The present invention provides the following [1] to [7]. [1] Fiber length 1.10 mm or less, volume weight 635 kg / m 3 Wood chips derived from Eucalyptus plants with a moisture content of 40% or less and a maximum moisture content of 40% or less. [2] Wood chips according to [1], having a lower heating value of 1800 kcal / kg or more at maximum moisture content. [3] Wood chips according to [1] or [2], wherein the Eucalyptus plant is a hybrid of Eucalyptus brassicae and Eucalyptus pelita. [4] The wood chips according to any one of [1] to [3], wherein the age of the Eucalyptus plant is 2 years or more and 15 years or less. [5] A wood chip mixture containing the wood chips according to any one of [1] to [4] and other wood chips. [6] A fuel containing at least one of the wood chips according to any one of [1] to [4] and the admixture according to claim 5. [7] The fuel according to [6], which is for heat utilization, power generation, or heat and electricity supply. [Effects of the Invention]

[0007] The present invention provides wood chips useful for applications such as fuel. The wood chips of the present invention have a specific volume weight, maximum moisture content, and fiber length within the specified ranges, resulting in a high combustion calorie per unit volume. This results in excellent utilization efficiency as fuel or other energy sources (e.g., boiler production efficiency), making them suitable for fuel. Furthermore, the wood chips of the present invention have a high volume weight and a low moisture content, resulting in a higher wood mass-to-weight ratio compared to conventional wood chips, improving transportation efficiency. Furthermore, since the wood chips of the present invention can be produced from wood with a high CO2 fixation capacity, mass production of the wood chips of the present invention at large-scale commercial plantations allows for efficient fixation of atmospheric carbon dioxide during the growth of the trees that serve as the raw material. Therefore, the wood chips of the present invention can contribute to the realization of a sustainable society by serving as a measure to mitigate global environmental change and curb global warming. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Wood chips] The wood chips of the present invention have a predetermined fiber length, bulk density, and maximum moisture content.

[0009] (Volume weight) The bulk density of wood chips is 635 kg / m 3 or more, preferably 640 kg / m 3 More preferably, 645 kg / m 3 More preferably, 650 kg / m 3 That's all. Wood whose bulk density satisfies the above numerical values ​​tends to have thick fiber walls and a structure with few voids. Most of the water in wood is present in the voids, and a structure with few voids can make it difficult for water to be absorbed. Furthermore, wood whose bulk density satisfies the above numerical values ​​can transport a larger amount of wood at one time for the same volume compared to wood that does not, thereby improving transportation efficiency. Furthermore, since wood can be produced from wood with a larger amount of carbon dioxide fixation, the mass production of such wood chips can increase the amount of carbon dioxide fixation, which can contribute to the realization of a sustainable society as a measure to mitigate global environmental change and curb global warming. The upper limit is usually 800 kg / m 3Less than or equal to 750 kg / m 3 Less than or equal to 730 kg / m 3 More preferably, 720 kg / m or less 3 The following is the result.

[0010] Volume weight is the ratio of weight to volume. Volume weight can be measured by placing wood chips in a measuring cylinder containing water, reading the increased scale, confirming the increase in volume, drying the chips, and measuring and calculating the bone-dry weight (JAPAN TAPPI No. 3:2000). The same measurement method is used in the examples below.

[0011] (Maximum moisture content) The maximum moisture content of the wood chips is 40% or less, preferably 39.5% or less, and more preferably 39% or less. While typical wood chips have a maximum moisture content higher than 40%, the wood chips of the present invention have a maximum moisture content and volume weight that satisfy the above values, resulting in a high calorific value and making them suitable for use as fuel. In addition, the low moisture content can improve transportation efficiency. There is no particular lower limit, but it is generally 35% or more.

[0012] The maximum moisture content is the maximum moisture content that can be contained in wood chips. The maximum moisture content can be measured by the following procedure. Wood chips (preferably 100 g or more) are soaked in water for at least two nights, and then the moisture on the chip surface is removed and the weight (weight (g) before drying) is measured. The wood chips are then dried in a blower dryer at 105°C for 48 hours, and the weight (weight (g) after drying) is measured. Each weight is substituted into the following formula to determine the maximum moisture content. Maximum moisture content (%) = (weight before drying - weight after drying) ÷ weight before drying × 100

[0013] (Lower heating value at maximum water content) The lower heating value of the wood chips at their maximum moisture content is preferably 1800 kcal / kg or more, more preferably 1900 kcal / kg or more. Because the wood chips of the present invention have a lower maximum moisture content than general wood chips, their lower heating value at their maximum moisture content is higher than that of general wood chips. The lower heating value of the wood chips when dry is not significantly different from that of general chips. Wood chips whose lower heating value at their maximum moisture content satisfies the above-mentioned values ​​can store a large amount of heat in a given volume, and can be used as fuel directly, or can obtain a large amount of combustion energy when processed into pellets and used as fuel. Furthermore, because a large amount of heat can be stored in a given volume, transportation and storage efficiency can be improved.

[0014] The lower heating value at maximum moisture content is expressed as the lower heating value per wet weight when the wood chips have absorbed water up to the maximum moisture content, and can be calculated using the following formula, and the measurement method in the examples below is also the same. Lower heating value at maximum water content (kcal / kg) = Anhydrous base lower heating value (kcal / kg) x solids content (%) ÷ 100 - latent heat of vaporization of water (kcal / kg) x retained moisture (kg) Latent heat of vaporization of water = 2,250 kJ / kg Solid content (%) = 100 - maximum moisture content (%)

[0015] The lower heating value (kcal / kg) on ​​an anhydrous basis can be determined by the following method. Wood chips were crushed in a grinder and sieved to 200 mesh or less to obtain wood flour as the sample. Nitrogen, carbon, and hydrogen contents were measured using an NCH analyzer in accordance with Coals and cokes - Methods for elemental analysis using instrumental analyzers (JIS M 8819). Values ​​other than these and ash content were calculated as oxygen content. Ash content was measured in accordance with Coals and cokes - Methods for proximate analysis (JIS M 8812). Higher heating values ​​were measured using a Shimadzu Nenken automatic bomb calorimeter (CA-4PJ) in accordance with Coals and cokes - Methods for measuring gross calorific value and calculating net calorific value using a bomb calorimeter (JIS M 8814), and lower heating values ​​were calculated taking into account the oxygen and ash content.

[0016] (fiber length) The fiber length of wood chips is 1.10 mm or less, preferably 1.05 mm or less, and more preferably 1.00 mm or less. Wood chips whose fiber length satisfies the above numerical values ​​and also satisfy the maximum moisture content and bulk density are useful as fuel. There is no particular lower limit, but it is usually 0.50 mm or more, preferably 0.55 mm or more, more preferably 0.60 mm or more, and even more preferably 0.65 mm or more.

[0017] The fiber length can be measured as a length-weighted average fiber length using a fiber tester (manufactured by Lorentzen & Wettre) in accordance with JIS P 8226:2011 "Pulp - Fiber length measurement method by optical automatic analysis method," and the measurement method in the examples below is the same.

[0018] (Trees) Wood chips are derived from woody plants. Woody plants are usually forest trees, and examples include broad-leaved trees such as eucalyptus, acacia, birch, and beech, and coniferous trees such as red pine, cedar, and cypress. Broad-leaved trees are preferred, more preferably Acacia and Eucalyptus plants, and even more preferably Eucalyptus plants. Eucalyptus plants grow quickly, resulting in a large yield of wood chips, making them suitable for fuel chips. Furthermore, after felling, reforestation by coppicing from stumps is possible, allowing for sustainable afforestation.

[0019] Examples of plants of the genus Eucalyptus include Eucalyptus pellita, Eucalyptus brassiana, Eucalyptus urophylla×Eucalyptus grandis, Eucalyptus pellita×Eucalyptus brassiana, Eucalyptus urophylla, Eucalyptus grandis, Eucalyptus maculata, Eucalyptus tereticornis, Eucalyptus camaldulensis, Eucalyptus rudis, Eucalyptus resinifera, Eucalyptus propinqua, Eucalyptus sideroxylon, Eucalyptus botryoides, Eucalyptus viminalis, Eucalyptus saligna, Eucalyptus ovata, Eucalyptus globulus, Eucalyptus nitens, Eucalyptus saligna, Eucalyptus cladocalyx, and hybrids of two or more tree species selected from these. Among these, species suitable for the environment of the plantation site can be selected (for example, when planting in the tropics, tree species that can be adapted to the tropics) and preferred are E. pellita, E. brassiana, E. urophylla, hybrids of E. brassiana and E. pellita, hybrids of E. urophylla and E. pellita, and hybrids of two or more tree species selected from these, with E. brassiana and E. pellita being more preferred. Both E. pellita and E. brassiana have relatively good bulk density and maximum moisture content, but there are also hybrids with even higher bulk density (for example, 550 kg / m 3 It is believed that by crossbreeding the above individuals and selecting the resulting F1 individuals, individuals with superior traits were obtained.

[0020] The plants from which wood chips are derived are usually planted trees grown from cloned seedlings or seedlings. There are no particular restrictions on the age of the trees, as long as they are old enough to produce wood chips (usually 2 years or older), preferably 5 years or older. There is no particular upper limit from the perspective of quality, but from an economical perspective, the shorter the age, the better. In the case of Eucalyptus plants, the age is usually 15 years or less, preferably 10 years or less, depending on the plantation area.

[0021] The wood chips may be wood chips derived from a single plant, or may be a combination of two or more wood chips derived from plants of different species and ages.

[0022] [Method for producing wood chips] Wood chips can be produced from their source plants (e.g., Eucalyptus plants) in a conventional manner. For example, after felling the plant, the bark is removed from the wood (trunk and branches), and the wood is cut or crushed to obtain chips.

[0023] [Wood chip size and use] The size of wood chips may be determined according to their intended use and is not particularly limited. For example, when wood chips are used as fuel, they can be adjusted as needed to match the specifications of the conveyor to the combustion unit. The size of the chips is generally related to the conveyability and combustion rate. Many conveying problems are caused by incompatibility between the conveyor and the chip size. Selecting chips of a size that matches the specifications of the conveyor for each combustion unit can avoid such problems. The size of the chips may be determined appropriately from the perspectives of preventing mechanical problems, suppressing the generation of abnormally high temperatures due to instantaneous combustion, suppressing conveyor clogging, and suppressing cutting losses. Wood chips may be pelletized as needed. Examples of uses for wood chips include fuel (e.g., power generation, heat utilization, and thermoelectric supply), pulp (e.g., paper pulp), wood boards (e.g., oriented strand board (OSB), particle board, and medium-density fiberboard (MDF)), paving, and agricultural uses (e.g., compost and mushroom beds), with fuel being preferred.

[0024] [Wood chip mixture] The above wood chips may be used in combination of two or more, or may be used in combination with other wood chips other than the above wood chips. Examples of other wood chips include wood chips that differ in at least one of fiber length, volume weight, and pulp yield. The blending ratio when combined with other wood chips can be appropriately determined depending on the application. Examples of sizes and applications of the wood chip mixture are the same as those of wood chips. The method for producing the wood chip mixture is not particularly limited as long as it includes a step of mixing the wood chips that make up the mixture to obtain the mixture. The mixing may be performed by a conventional method.

[0025] 〔fuel〕 The wood chips and admixtures can be used as fuels, for example, for power generation, heat utilization, and thermoelectric supply. When used as fuel, they may be used as is, or may be subjected to moisture adjustment treatment as necessary. The moisture adjustment treatment is a treatment in which the moisture content of the wood chips is preferably 55% or less, more preferably 35% or less, based on the weight of the wood. When used as fuel, the wood chips and admixtures may be used together with fuels other than wood chips.

[0026] 〔pulp〕 The wood chips and admixtures can be used as raw materials for pulp. The conditions or techniques for producing pulp are not particularly limited, as long as they include a step of pulping the wood chips or admixtures. Pulping methods include, but are not limited to, chemical methods (chemical pulping) that involve cooking, such as the kraft method, sulfite method, soda method, and polysulfide method; mechanical methods (mechanical pulping) that use equipment such as refiners and grinders; and methods of pulping by mechanical force after chemical pretreatment (semi-chemical pulping). Further treatments such as bleaching and beating may be performed. The resulting pulp may be unbleached (before bleaching), bleached (after bleaching), beaten, or unbeaten pulp. Examples of chemical pulps include sulfite pulp and kraft pulp, with kraft pulp being preferred.

[0027] 〔paper〕 Paper can be produced from pulp by conventional methods, such as a production method including a step of forming a sheet from pulp. Sheet formation can be performed, for example, according to Japanese Industrial Standards (JIS) P 8122, "Pulp - Method for Preparing Test Handsheets" (1989 edition), by forming pulp into a sheet using a paper machine. When forming pulp into a sheet, additives commonly used in papermaking applications can be added to the pulp. Examples of such additives include paper strength agents, bulking agents, pigments, retention aids, drainage aids, internal sizing agents (rosin-based sizing agents, aluminum sulfate, etc.), pH adjusters, antifoaming agents, pitch control agents, and slime control agents. The amount of such additives used is not particularly limited, and may be within a range that does not impair the effects of the present invention. When forming a sheet, paper raw materials other than pulp can also be used, such as rayon fibers and films. The paper raw material may be pulp obtained from the above-mentioned Eucalyptus plant together with other materials preformed into a shape such as a sheet, film, roll, etc. The paper raw material may contain pulp made from other plants, but preferably does not contain it.

[0028] Examples of papermaking machines include Fourdrinier papermaking machines, cylinder papermaking machines, gap formers, hybrid formers, multi-layer papermaking machines, and known papermaking machines that combine papermaking methods in two or more papermaking machines selected from these. The press line pressure in the papermaking machine and the calender line pressure in the case of calendering in a subsequent stage may both be set within ranges that do not impair operability and the properties of the plasticized cellulose obtained.

[0029] Paper can be used for various purposes, but it can be used as printing paper because it has good texture, improves ink receptivity during printing, and suppresses the occurrence of printing unevenness, making it suitable for printing.It can also be used as coated paper because it can suppress the occurrence of coating unevenness. [Example]

[0030] Examples 1 to 3 and Comparative Examples 1 to 3 Approximately 200,000 seedlings (seedlings) of Eucalyptus species, including species and hybrids suitable for tropical and subtropical regions, were prepared and planted in plantations in Brazil. Seedlings (age at planting: 100 days after cutting) were rooted in a greenhouse with a sprinkler system for approximately 100 days after sowing (approximately 3 weeks, high humidity (approximately 100%), shading), then acclimatized in a shading chamber (gradually decreasing shading and humidity), and finally planted in an outdoor field during the rainy season (late December to June) at a planting density of 1,666 plants / ha. After approximately 4 years of cultivation, the plants were selected based on volume and tree form, narrowing the selection to approximately 200 individuals. The selected individuals were then felled, and clonal plantings were propagated by cuttings from the sprouted branches. The clonal plantings were then transplanted to a sand-culture rack, where branches were allowed to grow as mother trees, and the branches were then propagated by cuttings. A second planting test was then conducted using clone seedlings (30 trees per line). After four years of cultivation, the volume, tree form, and uniformity of the clones were checked, and the selection was narrowed down to 40 clones. Large-scale cutting propagation was then carried out using mother trees grown in sand culture racks, and a third large-scale planting test was conducted using clone seedlings (500 trees per line). After four years of cultivation, the volume, tree form, uniformity, and disease suitability of the clones were evaluated over a large area, and the selection was narrowed down to 10 clones. A pulping suitability test based on TAPPI JAPAN was then conducted to select several clones. This process was repeated for five years, and selection was carried out from a total of one million individuals, resulting in the selection of six clones.

[0031] [Physical properties of wood chips] The bark was removed from the wood of each clone and cut into wood chips. The physical properties of each wood chip were measured under the following conditions (Table 1).

[0032] (fiber length) The length-weighted average fiber length was measured using a fiber tester (Lorentzen & Wettre) in accordance with JIS P 8226:2011 "Pulp - Fiber length measurement method by optical automatic analysis."

[0033] (Volume weight) Measurements were made in accordance with J TAPPI No. 3:2000 "Wood chips - volume weight test method."

[0034] (Lower heating value at maximum moisture content, maximum moisture content) The measurements were performed using the procedure described above. The calorific value was measured using a Nippon Kenken automatic bomb calorimeter CA-4AJ measurement system (Shimadzu Corporation).

[0035] [Table 1]

[0036] [Measurement of moisture content behavior of wood chips over time] The moisture content behavior of wood chips from each clone in Example 1 and Comparative Examples 1 to 3 was measured. First, 300 BDg (bone dry weight) of each chip was immersed in water for at least two nights, and the moisture content at saturation was measured. The chips were then left to stand in an environment of 30°C and 76% RH (relative humidity), and the moisture content was measured every day (Table 2). The moisture content after 0 days corresponds to the maximum moisture content.

[0037] [Table 2]

[0038] It was clear that the chips of Example 1 took a shorter time to reach the air-dry moisture content (air-dry state) and dried earlier than those of Comparative Examples 1 to 3. The above results are based on the present invention, where the fiber length is 1.10 mm or less and the density is 635 kg / m 3 It is clear that wood chips with a maximum moisture content of 40% or less exhibit good fuel properties.

Claims

1. Fiber length 1.10 mm or less, volume weight 635 kg / m 3 and a maximum moisture content of 40% or less.

2. 2. The wood chips according to claim 1, which have a lower heating value of 1800 kcal / kg or more at the maximum moisture content.

3. 3. The wood chips according to claim 1 or 2, wherein the Eucalyptus plant is a hybrid of Eucalyptus brassiana and Eucalyptus pelita.

4. The wood chips according to any one of claims 1 to 3, wherein the age of the Eucalyptus plant is 2 years or more and 15 years or less.

5. A wood chip mixture comprising the wood chips according to any one of claims 1 to 4 and other wood chips.

6. A fuel comprising at least one of the wood chips according to any one of claims 1 to 4 and the admixture according to claim 5.

7. The fuel according to claim 6, which is for heat utilization, power generation or heat and electricity supply.

Images