Method for producing solid fuel

Abstract

The present invention provides a method for producing a solid fuel that uses woody biomass as a raw material, has a reduced chlorine content and potassium content, has crushability equivalent to that of coal, and can be used as fuel for pulverized coal boilers by mixing with coal and crushing it. Solid fuel is produced by a method including the steps of washing pulverized woody biomass material of 50 mm or less with at least 1.5 L / kg (bone dry weight of pulverized woody biomass material) of water, drying the pulverized woody biomass material after washing it with water, and roasting the dried pulverized woody biomass material under conditions of an oxygen concentration of 10% or less and a material temperature of 240 to 350°C.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a solid fuel having a low chlorine content and a low potassium content by washing pulverized woody biomass with water, drying it, and then roasting it. [Background technology]

[0002] In recent years, the use of biomass-based fuels has been considered as a countermeasure against 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. Various methods for effectively utilizing biomass have been proposed. Among these, a useful method for converting biomass into high-value-added products at low cost is the carbonization of biomass to produce solid fuel. In this method, biomass is introduced into a carbonization furnace and heated for a predetermined period of time in an oxygen-deficient atmosphere to produce solid fuel.

[0003] The solid fuel produced in this way is used as fuel for combustion facilities such as power generation facilities and incineration facilities, and in this case, the solid fuel may be finely pulverized and used as pulverized fuel to improve combustion efficiency. Solid fuel is pulverized alone or mixed with coal, but since woody biomass is mostly fibrous, it is difficult to pulverize, resulting in problems such as reduced combustion efficiency and reduced operability of the pulverizer.

[0004] Patent Document 1 discloses a method of pyrolyzing woody biomass such as waste lumber, thinned wood, garden trees, and construction waste at a temperature of 240°C to 300°C for 15 to 90 minutes, followed by crushing. Heating temperatures below 240°C do not improve crushability, while temperatures above 300°C are undesirable because they increase the amount of submicron-order fine powder during crushing and crushing, making powder problems more likely to occur.

[0005] Patent Document 2 also discloses a method for producing solid fuel with crushability 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 processing temperature of 350 to 400°C for 30 to 90 minutes.

[0006] Solid fuels obtained from biomass containing chlorine compounds have a high chlorine content, and such solid fuels require measures to prevent corrosion of combustion equipment and exhaust gas treatment equipment. Therefore, it is necessary to reduce the chlorine content of solid fuels. Patent Document 3 discloses a method for washing solid fuels with water to reduce the chlorine content of solid fuels produced by roasting raw materials containing biomass. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-26474 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-191085 [Patent Document 3] Special Publication No. 2009-540097 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0008] However, solid fuels obtained from biomass containing chlorine compounds have a high chlorine content, making them difficult to use as boiler fuel. Therefore, post-processing to reduce the chlorine content, measures to prevent corrosion of combustion equipment, and exhaust gas treatment equipment are required, which increases costs. [Means for solving the problem]

[0009] The present inventors have investigated a technology for simply and efficiently producing solid fuel with reduced chlorine content from woody biomass, and have found that solid fuel with reduced chlorine content and reduced potassium content can be efficiently produced by crushing woody biomass, washing the crushed material with water to dehydrate it, and then roasting it, which has led to the completion of the present invention.

[0010] That is, the present invention provides the following inventions. (1) Washing woody biomass pulverized material of 50 mm or less in water at a rate of 1.5 L / kg (bone dry weight of woody biomass pulverized material); a step of washing the pulverized woody biomass with water and then drying it; Roasting the dried pulverized woody biomass under conditions of an oxygen concentration of 10% or less and a material temperature of 240 to 350°C; A method for producing a solid fuel, comprising: (2) Washing woody biomass pulverized material of 50 mm or less in running water at a rate of 0.33 L / min kg (bone dry weight of woody biomass pulverized material) for 5 minutes or more; a step of washing the pulverized woody biomass with water and then drying it; Roasting the dried pulverized woody biomass under conditions of an oxygen concentration of 10% or less and a material temperature of 240 to 350°C; A method for producing a solid fuel, comprising: (3) The method for producing a solid fuel according to (1) or (2), wherein the woody biomass is of the genus Eucalyptus. (4) The method for producing a solid fuel according to (1) or (2), wherein the woody biomass is Hevea brasiliensis. (5) The method for producing a solid fuel according to any one of (1) to (4), wherein the solid fuel is mixed with coal, pulverized, and then burned together with the coal. [Effects of the Invention]

[0011] According to the present invention, a solid fuel having a reduced chlorine content and a reduced potassium content can be produced. In other words, there is no need for post-treatment to reduce the chlorine content and the potassium content of the solid fuel, nor for measures against corrosion of the combustion equipment or for exhaust gas treatment equipment. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention is a method for producing solid fuel, comprising the steps of washing pulverized woody biomass with water, drying the pulverized woody biomass after washing with water, and roasting the dried pulverized woody biomass.

[0013] The wood used as the raw material for the woody biomass of the present invention may be, for example, either a broad-leaved tree or a coniferous tree.Specific examples of broad-leaved trees include eucalyptus, rubber tree, beech, Chinese linden, white birch, poplar, acacia, oak, sugar maple, Asiatic elm, paulownia, magnolia, willow, ash, phillyraeoides phillyraeoides, oak, sawtooth oak, horse chestnut, zelkova, beech, dogwood, and ash. Examples of conifers include cedar, spruce, larch, black pine, Abies sachalinensis, Himekomatsu, yew, juniper, spruce, Japanese spruce, Japanese holly, Japanese holly, fir, Japanese yew, Douglas fir, Asunaro, cypress, Japanese hemlock, Japanese hemlock, Hinoki, yew, Inugaya, spruce, yellow cedar, Douglas fir, Sitka spruce, Radiata pine, Eastern spruce, Eastern white pine, Western larch, Western fir, Western hemlock, and tamarack.

[0014] Among these, the genus Eucalyptus and the rubber tree (Hevea brasiliensis) are preferred. Examples of the genus Eucalyptus include Eucalyptus (hereinafter abbreviated as E.) calophylla, E. citriodora, E. diversicolor, E. globulus, E. grandis, E. urograndis, E. gummifera, E. marginata, E. nesophila, E. nitens, E. amygdalina, E. camaldulensis, E. delegatensis, E. gigantea, E. muelleriana, E. obliqua, E. regnans, E. sieberiana, E. viminalis, and E. marginata.

[0015] In the present invention, woody biomass must be pulverized to a size of 50 mm or less, and it is more preferable to use pulverized woody biomass with a size of 0.1 to 50 mm. In the present invention, the size of the pulverized woody biomass refers to the size of the circular holes in a sieve. As an apparatus for pulverizing woody biomass, a knife-cutting type biomass fuel chipper is preferably used for the pulverization process.

[0016] Before washing the pulverized woody biomass with water, the pulverized woody biomass may be immersed in 5 L or more of water per 1 kg of bone dry weight of the pulverized woody biomass.

[0017] When washing the pulverized woody biomass with water, the amount of water must be at least 1.5 L / kg (bone-dry weight of the pulverized woody biomass), and may be at least 15 L / kg (bone-dry weight of the pulverized woody biomass). If the amount of washing water is less than 1.5 L / kg (bone-dry weight of the pulverized woody biomass), the chlorine and potassium contents of the resulting solid fuel will not be sufficiently reduced. There is no particular upper limit to the amount of washing water, but it can be set to 500 L / kg (bone-dry weight of the pulverized woody biomass) or less. Note that the chlorine and potassium concentrations of the water used for washing are preferably as low as possible, and the chlorine and potassium concentrations are preferably 0.1% by mass or less.

[0018] When washing pulverized woody biomass with running water, wash for at least 5 minutes with running water at a rate of at least 0.33 L / min kg (bone dry weight of pulverized woody biomass). The washing time can also be 60 minutes or longer.

[0019] In addition, a dehydration step may be performed after washing the pulverized woody biomass with water. As a dehydration device, a pressurized solid-liquid separator such as a screw press, filter press, belt press, or reciprocating press can be preferably used.

[0020] After washing with water, the pulverized woody biomass must be dried, preferably to a moisture content of 10% or less.

[0021] Torrefaction in the present invention refers to a process in which wood is heated in a low-oxygen atmosphere at a temperature lower than that of the so-called carbonization process. While the temperature for the normal carbonization process of wood is 400 to 700°C, torrefaction is carried out at a lower temperature. By torrefaction, a solid fuel having a higher energy density than the starting material is obtained.

[0022] The roasting conditions in the present invention are an oxygen concentration of 10% or less and a material temperature of 240 to 350°C. Here, material temperature refers to the temperature of woody biomass during roasting. When the oxygen concentration exceeds 10%, the material yield and calorific yield decrease. Furthermore, when the material temperature is below 240°C, the crushability described below is insufficient, and when it exceeds 350°C, the material yield and calorific yield decrease. The material temperature is preferably 240 to 330°C, and more preferably 250 to 320°C. Hemicellulose undergoes significant thermal decomposition around 270°C, while cellulose and lignin undergo significant thermal decomposition around 355°C and 365°C, respectively. Therefore, it is presumed that by setting the roasting temperature to 240 to 350°C, hemicellulose is preferentially pyrolyzed, making it possible to produce a solid fuel that achieves both material yield and crushability.

[0023] In the present invention, the roasting treatment apparatus is not particularly limited, but a rotary kiln or a vertical furnace is preferred. It is preferable to replace the atmosphere in the apparatus with an inert gas such as nitrogen to adjust the oxygen concentration to 10% or less. The treatment time is preferably 15 to 180 minutes.

[0024] The solid fuel obtained by the present invention has a material yield of 60 to 95% and a calorific yield of 70 to 95% relative to the raw material woody biomass. Furthermore, the Hardgrove Crushability Index (HGI) specified in JIS M 8801:2004, which is an index of crushability, is preferably 30 or more, more preferably 40 or more. The higher the HGI, the easier it is to crush. If the HGI is in the range of 30 to 70, it can be mixed with coal and crushed. Since the HGI of coal is usually 40 to 70, the solid fuel obtained by the present invention has crushability equivalent to that of coal.

[0025] 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]

[0026] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0027] Example 1 Chips of Eucalyptus camaldulensis, from which the bark had been removed, were crushed in a knife-cutting type biomass fuel chipper (Midorisan Co., Ltd., Wood Hacker MEGA360DL) and passed through a 50 mm screen to obtain a crushed material.

[0028] The crushed material was washed for 5 minutes with running water at 0.33 L / min kg (crushed material bone dry weight) for 1 kg of bone dry solids (1.65 L of water for 1 kg of bone dry solids), and then dewatered using a Buchner funnel. The dewatered solids were dried in a dryer at 120 °C until the moisture content reached 10%. Next, a large kiln-type carbonization furnace was used, purged with nitrogen, and roasted to a material temperature of 260 °C for 20 minutes to obtain solid fuel.

[0029] Example 2 Solid fuel was obtained in the same manner as in Example 1, except that the crushed material was washed for 10 minutes with running water at 0.33 L / min·kg (crushed material bone dry weight) per 1 kg of bone dry solids (washed with 3.30 L of water per 1 kg of bone dry solids).

[0030] Example 3 Solid fuel was obtained in the same manner as in Example 1, except that the crushed material was washed with running water at 0.33 L / min·kg (crushed material bone dry weight) for 30 minutes per 1 kg of bone dry solids (washed with 9.9 L of water per 1 kg of bone dry solids).

[0031] Example 4 Solid fuel was obtained in the same manner as in Example 1, except that the crushed material was washed with running water at 0.33 L / min·kg (crushed material bone dry weight) for 60 minutes per 1 kg of bone dry solids (washed with 19.8 L of water per 1 kg of bone dry solids).

[0032] Example 5 Solid fuel was obtained in the same manner as in Example 1, except that the crushed material was washed with running water at 0.33 L / min·kg (crushed material bone dry weight) for 180 minutes per 1 kg of bone dry solids (washed with 59.4 L of water per 1 kg of bone dry solids).

[0033] Example 6 Solid fuel was obtained in the same manner as in Example 1, except that the crushed material was washed with running water at 0.33 L / min·kg (crushed material bone dry weight) for 360 minutes per 1 kg of bone dry solids (washed with 118.8 L of water per 1 kg of bone dry solids).

[0034] Example 7 Solid fuel was obtained in the same manner as in Example 1, except that the crushed material was washed with running water at 0.33 L / min·kg (crushed material bone dry weight) for 540 minutes per 1 kg of bone dry solids (washed with 178.2 L of water per 1 kg of bone dry solids).

[0035] Example 8 Solid fuel was obtained in the same manner as in Example 1, except that the crushed material was washed with running water at 0.33 L / min·kg (crushed material bone dry weight) for 1,440 minutes per 1 kg of bone dry solids (washed with 475.2 L of water per 1 kg of bone dry solids).

[0036] Comparative Example 1 A solid fuel was obtained in the same manner as in Example 1, except that the pulverized material was not washed.

[0037] Comparative Example 2 Solid fuel was obtained in the same manner as in Example 1, except that the crushed material was washed for 1 minute with running water at 0.33 L / min·kg (crushed material bone dry weight) per 1 kg of bone dry solids (washing with 0.33 L of water per 1 kg of bone dry solids).

[0038] The washed pulverized wood chips obtained in Examples 1 to 8 and Comparative Examples 1 and 2, and the solid fuels after roasting treatment were measured for the following items. The results are shown in Tables 1 and 2. Chlorine content: Samples were dried at 105°C for 24 hours, and the chlorine concentration was measured by ion chromatography in accordance with JIS Z 7302-6, and calculated based on this. Potassium content: 10 g of a sample dried at 105°C for 24 hours was taken and crushed for 30 seconds using a Wonder Crusher (WC-3L, manufactured by Osaka Chemical Co., Ltd.). The resulting powder sample was analyzed using an X-ray fluorescence analyzer (Niton TM Measurements were performed using an XL3t XRF Analyzer (manufactured by Thermo Fisher Scientific).

[0039] [Table 1]

[0040] [Table 2]

[0041] As shown in Tables 1 and 2, it was possible to reduce the chlorine and potassium concentrations of the ground wood chips by washing with 1.5 L / kg (bone-dry weight of ground wood biomass) or more of water. Furthermore, roasting the ground wood chips after washing with water made it possible to further reduce the chlorine concentration.

[0042] Example 9 A solid fuel was obtained in the same manner as in Example 1, except that Eucalyptus camaldulensis bark was used as the raw material.

[0043] Example 10 A solid fuel was obtained in the same manner as in Example 2, except that Eucalyptus camaldulensis bark was used as the raw material.

[0044] Example 11 A solid fuel was obtained in the same manner as in Example 3, except that Eucalyptus camaldulensis bark was used as the raw material.

[0045] Example 12 A solid fuel was obtained in the same manner as in Example 4, except that Eucalyptus camaldulensis bark was used as the raw material.

[0046] Example 13 A solid fuel was obtained in the same manner as in Example 5, except that Eucalyptus camaldulensis bark was used as the raw material.

[0047] Example 14 A solid fuel was obtained in the same manner as in Example 6, except that Eucalyptus camaldulensis bark was used as the raw material.

[0048] Example 15 A solid fuel was obtained in the same manner as in Example 7, except that Eucalyptus camaldulensis bark was used as the raw material.

[0049] Example 16 A solid fuel was obtained in the same manner as in Example 8, except that Eucalyptus camaldulensis bark was used as the raw material.

[0050] Comparative Example 3 A solid fuel was obtained in the same manner as in Comparative Example 1, except that Eucalyptus camaldulensis bark was used as the raw material.

[0051] Comparative Example 4 A solid fuel was obtained in the same manner as in Comparative Example 2, except that Eucalyptus camaldulensis bark was used as the raw material.

[0052] The chlorine content and potassium content of the bark pulverized materials after washing and the solid fuels after roasting treatment obtained in Examples 9 to 16 and Comparative Examples 3 and 4 were measured. The results are shown in Tables 3 and 4.

[0053] [Table 3]

[0054] [Table 4]

[0055] As shown in Tables 3 and 4, it was possible to reduce the chlorine and potassium concentrations of the bark pulverized material by washing with 1.5 L / kg (bone dry weight of pulverized woody biomass material) or more of water. Furthermore, roasting the pulverized bark material after washing with water made it possible to further reduce the chlorine concentration.

Claims

1. A method for producing a solid fuel from woody biomass of Eucalyptus or Hevea brasiliensis, which is mixed with coal, pulverized, and then mixed and burned with the coal, comprising the steps of: (a) washing woody biomass pulverized material having a size of 50 mm or less with water; (b) drying the pulverized woody biomass washed with water; (c) roasting the dried pulverized woody biomass under conditions of an oxygen concentration of 10% or less and a material temperature of 240 to 350°C; wherein the woody biomass includes bark, and in the washing step, the pulverized woody biomass is washed for 60 minutes or more with running water at a rate of 0.33 L / min kg or more per bone dry weight of the pulverized woody biomass.

2. The method of claim 1 , wherein the woody biomass is Eucalyptus.

3. 2. The method of claim 1, wherein the woody biomass is Hevea brasiliensis.

4. 4. The method according to claim 1, wherein the solid fuel is used in a coal boiler and has a Hardgrove Crushability Index of 30 to 70.

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