Method for solubilizing biomass feedstock

Abstract

To provide a solubilization treatment method for a biomass raw material capable of improving the yield of a water-soluble component.SOLUTION: The method for solubilizing a biomass feedstock includes a crushing step 2 of crushing the biomass feedstock containing cellulose and lignin charged into a crushing chamber of a crusher without applying heat from the outside.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for solubilizing a biomass raw material. [Background technology]

[0002] In recent years, technology to produce biomass fuel from non-food biomass (cellulosic biomass) such as wood, grass, and rice straw has been attracting attention as an alternative to food biomass such as sugarcane and corn.

[0003] Patent Document 1 describes a solubilization method for biomass raw materials, in which a cellulose-containing biomass raw material is pulverized under heating at 100° C. or higher but lower than 300° C., and water-soluble components are extracted with water. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-111034 Summary of the Invention [Problem to be solved by the invention]

[0005] Cellulosic biomass raw materials contain lignin in addition to cellulose. The present inventors discovered that by heating and pulverizing biomass raw materials, not only cellulose but also lignin can be decomposed into water-soluble components. However, in the solubilization method of Patent Document 1, the biomass raw materials are heated and pulverized at high temperatures, so the mixture of oligosaccharides and lignin obtained by decomposing cellulose into smaller molecules is easily denatured by heat. For this reason, there is a problem in that the yield of water-soluble components decreases when the heating and pulverization is performed for a certain period of time or longer.

[0006] Therefore, there is a need for a solubilization method for biomass raw materials that can improve the yield of water-soluble components. [Means for solving the problem]

[0007] The method for solubilizing a biomass raw material according to the present invention includes a crushing step in which a biomass raw material containing cellulose and lignin is placed in a crushing chamber of a crusher and crushed without applying heat from the outside.

[0008] This configuration pulverizes biomass feedstock without applying external heat, thereby suppressing thermal denaturation of the mixture of oligosaccharides and lignin during the solubilization process. This allows for easy adjustment of the solubilization process time, since the yield of water-soluble components remains constant even when the pulverization process is continued for a certain period of time. Furthermore, since no heating is required, the pulverizer's configuration can be simplified. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a process block diagram of a solubilization treatment of biomass raw materials. [Figure 2] 1 is a graph showing the pulverization time and solubilization rate when heat pulverization was performed. [Figure 3] FIG. 1 is a schematic diagram of the Voigt model. [Figure 4] 1 is a graph showing the medium collision energy per unit time and the solubilization rate according to an example. [Figure 5] 1 is a graph showing the grinding time and solubilization rate according to an example. [Figure 6] 1 is a graph showing the drying temperature and solubilization rate according to an example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the method for solubilizing biomass feedstock according to the present invention will be described with reference to the drawings. Note that the embodiments described below are merely examples for explaining the present invention, and the present invention is not limited to these embodiments. Therefore, the present invention can be implemented in various forms without departing from the gist of the present invention.

[0011] [Solubilization Treatment Method] The solubilization method for biomass raw materials according to the present invention will be described with reference to Figure 1. The solubilization method for biomass raw materials includes a drying step 1 in which the biomass raw material is dried to reduce the moisture content, a crushing step 2 in which the biomass raw material is crushed, and an extraction step 3 in which soluble components (extract) are extracted with water from the crushed material obtained in the crushing step 2.

[0012] The biomass raw material in the present invention is a biomass raw material containing cellulose, oligosaccharides, and lignin. Examples of such biomass raw materials include grass or plant biomass such as rice straw, wheat straw, and bagasse; thinnings such as bamboo and bamboo grass; wood processing waste such as sawdust, chips, and scraps; woody biomass such as roadside tree pruning, wooden building waste, bark, and driftwood; and cellulose products such as waste paper. Sludge, livestock manure, agricultural waste, and urban waste can also be used as long as they contain cellulose, lignin, oligosaccharides, and the like to an extent that they can be used as biomass raw materials. These biomass raw materials may be used alone or in combination with multiple different types. For example, in addition to lignin and oligosaccharides, they may also contain polysaccharides such as starch, hemicellulose, and pectin.

[0013] The biomass raw material may be coarsely pulverized to particles of approximately 1 mm to 100 mm in a coarse pulverization step before being dried in the drying step 1. Coarse pulverization allows the biomass raw material to be formed into a shape that is easy to handle. In the coarse pulverization step, a pulverization method can be selected depending on the form of the biomass raw material, and for example, a general-purpose pulverizer such as a hammer mill, cutter mill, vibration mill, ball mill, rod mill, roller mill, colloid mill, disk mill, or jet mill can be used. Furthermore, the pulverization treatment in the coarse pulverization step can be either a dry or wet method, but dry pulverization is preferable in terms of reducing the crystallinity of cellulose.

[0014] The coarsely pulverized biomass material is dried in drying step 1. Whether or not to perform drying step 1 may be determined by measuring the moisture content of the biomass material and determining the moisture content. In drying step 1, the moisture content of the biomass material is preferably 20% by mass or less, more preferably 10% by mass or less. The moisture content of the biomass material may be 0% by mass, but since prolonged drying is uneconomical, it is preferable that the moisture content be 3% by mass or more. Drying step 1 may be performed by natural drying, or by heating the biomass material with hot air drying or an electric heater. The coarse pulverization step may be performed after the moisture content of the biomass material is reduced to the above-mentioned value or less. By dry-pulverizing biomass material with a low moisture content, the crystallinity of cellulose and lignin can be efficiently reduced. Note that drying step 1 may be omitted.

[0015] The biomass raw material that has been coarsely pulverized in the coarse pulverization step or whose moisture content has been adjusted in the drying step 1 is pulverized in the pulverization step 2.

[0016] The mill used in the milling step 2 can be, for example, a ball mill such as a planetary ball mill, or a mill with a milling medium such as a rod mill or a vibrating mill. The biomass raw material is subjected to a mechanochemical effect by the milling force from the milling medium, and is broken down into components such as cellulose and lignin, resulting in a decrease in crystallinity and a decrease in molecular weight. This solubilization process of biomass raw materials is safe from a manufacturing perspective and has a low environmental impact because it does not use chemicals such as sulfuric acid.

[0017] The present inventors discovered that, as described in Patent Document 1, when biomass raw materials are pulverized while being heated in the pulverization step 2, the solubilization rate decreases over a certain period of time, as shown in Figure 2. Figure 2 is a graph plotting the solubilization rate versus pulverization time for biomass raw materials solubilized under the same heating and pulverization conditions, except that the pulverizer rotation speed was set to 1200 rpm, 1300 rpm, and 1400 rpm. Here, the "solubilization rate" refers to the ratio of the amount of carbon contained in water-soluble components to the amount of carbon contained in sugars such as cellulose, hemicellulose, and oligosaccharides contained in the biomass raw material (water-soluble organic carbon amount / carbon amount contained in the carbohydrates contained in the raw material). The decrease in solubilization rate shown in Figure 2 is thought to be caused by the heat-induced denaturation and insolubilization of the mixture of oligosaccharides and lignin produced by the heat pulverization. Therefore, in the pulverization step 2 of the present invention, the biomass raw material introduced into the pulverizer chamber is pulverized without external heat application to prevent the insolubilization of the mixture of oligosaccharides and lignin. The phrase "without applying heat from the outside" does not include a mode in which the inside of the grinding chamber is heated by an external device or a mode in which the inside of the grinding chamber is heated by a device mounted on the grinder.

[0018] In the pulverization step 2, even if no heat is applied to the biomass raw material from the outside, the temperature inside the pulverization chamber will rise due to collisions and friction of the pulverization media. Therefore, to prevent heat from being applied to the biomass raw material, the temperature inside the pulverization chamber should be kept below 120°C, preferably below 100°C. Furthermore, to activate the molecular motion of cellulose and the like, the temperature inside the pulverization chamber should be above 20°C. The pulverizer may be equipped with a temperature control device, a cooling device, or the like to maintain a constant temperature inside the pulverization chamber.

[0019] In the pulverization step 2 of this embodiment, since heating of the biomass raw material is not required, the configuration of the pulverizer can be simplified. In addition, since the sudden decrease in the solubilization rate as shown in Figure 2 can be suppressed, adjustment of the pulverization time, etc. can be easily performed.

[0020] In the pulverization step 2, the medium collision energy E per unit time in the pulverization chamber w It is recommended that the crushing be performed so that the medium collision energy E is 3 J / s or more. w is a value calculated by simulating the movement of the grinding media in the grinding chamber using the discrete element method. w The calculation method for the medium collision energy E will be described later. w If the flow rate is 3 J / s or more, water-soluble components can be efficiently obtained from the biomass raw material.

[0021] In extraction step 3, water-soluble components are extracted from the pulverized material obtained in pulverization step 2. In extraction step 3, it is desirable to add and mix water in an amount 0.1 to 500 times the amount of water as the pulverized material obtained in pulverization step 2, and then perform solid-liquid separation in a solid-liquid separator to obtain water-soluble components (extract) and a residue. Examples of solid-liquid separators include devices that use gravity sedimentation, centrifugation, membrane separation, coagulation separation, and flotation separation methods.

[0022] The solubilized solution containing the water-soluble components obtained in extraction step 3 may be subjected to total organic carbon measurement, constituent sugar analysis, NMR, GC-MS, etc. to identify the components contained therein. The solubilization rate may also be determined from the measurement of total organic carbon.

[0023] The solubilized solution may be mixed with a solid acid catalyst and stirred to hydrolyze it, producing a saccharified solution containing monosaccharides such as glucose as the main component. The saccharified solution thus obtained can be fermented or distilled to produce ethanol, a biomass fuel. Furthermore, the lignin contained in the solubilized solution may be chemically modified and used as a plastic material.

[0024] [Medium collision energy] The media collision energy E per unit time in the grinding chamber is w The calculation method for the medium collision energy E wis obtained based on a simulation of the movement of grinding media using the discrete element method (DEM). The discrete element method is a method that models the contact forces, such as elastic repulsive force and friction force, that act between grinding media in contact with each other, and numerically analyzes the movement of individual particles that are affected by the contact force based on their respective equations of motion.

[0025] Collisions between grinding media or between grinding media and the grinding chamber wall in the grinding chamber are represented by the Voigt model shown in Figure 3. In the normal direction of the grinding media, a spring 11 representing the elastic properties of the spherical particles 10 used as grinding media and a dashpot 12 representing the inelastic properties are connected in parallel to represent the force acting on the grinding media. In the tangential direction of the grinding media, in addition to the spring 11 and dashpot 12, a friction slider 13 is inserted to represent the friction force accompanying contact of the grinding media.

[0026] If the grinding media are hemispherical spheres of size r, the normal compressive force F acting between the grinding media is n is the tangential shear force F in equation (1). t is given by equation (2), where K is the elastic coefficient, η is the viscous coefficient, u is the relative displacement, φ is the relative angular displacement, μ p is the friction coefficient between the grinding media, and the subscripts n and t represent the normal and tangential directions, respectively.

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[0027] Elastic modulus K in the normal direction when grinding media contact each other n is given by equations (3) to (5) using the Young's modulus E and Poisson's ratio ν of the grinding media and grinding chamber wall according to Hertz's elastic contact theory. The subscripts i and j represent one grinding media i and one grinding media j colliding with one grinding media i, respectively.

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[0028] Elastic modulus K in the normal direction when the grinding media contacts the grinding chamber wall n is given by equations (6) to (7), where the subscript w represents the grinding chamber wall.

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[0029] Tangential elastic modulus K t can be obtained based on the definition of the Lame constant in equation (8), which expresses the relationship between the shear modulus and Young's modulus of a material.

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[0030] In addition, in the vibration equation of one degree of freedom with an elastic spring and a viscous dashpot, the viscosity coefficient η ij is given by equation (9), where m is the mass of the grinding media.

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[0031] Simulation using the discrete element method makes it possible to obtain information on the motion of the grinding media in the grinding chamber, such as the number of collisions of the grinding media, kinetic energy, contact force between the grinding media, and the motion trajectory of the grinding media, in any time and space. Therefore, the media collision energy E per unit time Δt of the grinding media in the grinding chamber can be calculated as follows: w is expressed by equation (10), where n represents the number of collisions. Also, as shown in equation (11), vij represents the relative velocity between the grinding media or between the grinding media and the grinding chamber wall at the time of collision. n is v ij The normal component of v t is v ij and the tangential components of

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[0032] In the above case, only the collision energy when grinding medium i collides with grinding medium j is considered, and the collision energy when grinding medium j collides with grinding medium i at that time is ignored. In addition, prediction of phenomena such as the collision and grinding of biomass raw materials in the grinding chamber is not included.

[0033] Medium collision energy E w The value of varies depending on the mass of the grinding media, the rotation speed of the grinding machine, etc. Therefore, the media collision energy E w By setting the grinding conditions so that the pulverization rate is 3 J / s or more, it becomes possible to efficiently produce water-soluble components.

[0034] [Example] Examples of the present invention will be described below, but the present invention is not limited to the descriptions of these examples.

[0035] Example 1 Using 0.15 g of sugarcane bagasse containing cellulose and lignin as the biomass feedstock, water-soluble components were obtained using the biomass feedstock solubilization method described above. In the drying step 1, the sugarcane bagasse was dried at 150°C for 3 hours to a moisture content of 8.77%, followed by the crushing step 2 for 180 minutes. In the crushing step 2, a ball mill (5 mm diameter ball, 75 g) was used as the crusher, and crushing was performed at a rotation speed of 100 rpm. The temperature of the sugarcane bagasse during crushing was 40°C to 80°C. The crushed material obtained in the crushing step 2 was then mixed with 10 times the amount of water, and the solubilized solution was obtained by solid-liquid separation using a solid-liquid separator. The solubilization rate was then calculated. The solubilization rate was determined by the sugar content of the biomass feedstock calculated by constituent sugar analysis and the total organic carbon content of the solubilized solution measured as the amount of water-soluble organic carbon using a TOC analyzer (total organic carbon analyzer).

[0036] In addition, a simulation was performed using the discrete element method under the conditions in which the pulverization process 2 was performed, and the medium collision energy E per unit time in the pulverization process 2 of Example 1 was calculated. w was calculated.

[0037] Example 2 A solubilized solution was obtained in the same manner as in Example 1, except that the rotation speed of the ball mill was set to 200 rpm and the pulverization step 2 was carried out for 180 minutes. w was calculated.

[0038] Example 3 A solubilized solution was obtained in the same manner as in Example 1, except that the rotation speed of the ball mill was set to 300 rpm and the pulverization step 2 was carried out for 180 minutes. w was calculated.

[0039] Example 4 A solubilized solution was obtained in the same manner as in Example 1, except that the rotation speed of the ball mill was set to 400 rpm. w was calculated.

[0040] Example 5 A solubilized solution was obtained in the same manner as in Example 1, except that the rotation speed of the ball mill was set to 500 rpm and the pulverization step 2 was carried out for 60 minutes, 120 minutes, 180 minutes, and 300 minutes. w was calculated.

[0041] Example 6 A solubilized solution was obtained in the same manner as in Example 1, except that the rotation speed of the ball mill was set to 600 rpm and the pulverization step 2 was carried out for 30 minutes, 60 minutes, 120 minutes, and 180 minutes. w was calculated.

[0042] Example 7 A solubilized solution was obtained in the same manner as in Example 1, except that the rotation speed of the ball mill was set to 700 rpm and the pulverization step 2 was performed at 0, 15, 30, 60, 120, and 180 minutes. w was calculated.

[0043] Example 8 A solubilized solution was obtained in the same manner as in Example 1, except that the drying step 1 was not carried out, and the pulverization step 2 was carried out for 180 minutes at a ball mill rotation speed of 600 rpm.

[0044] Example 9 A solubilized solution was obtained in the same manner as in Example 8, except that the drying time in drying step 1 was 30 minutes, the drying temperatures were 50°C, 100°C, and 150°C, and the pulverization step 2 was carried out for 180 minutes. The weight loss rate due to moisture loss in the biomass raw material was 3.45% when the drying temperature was 50°C, 6.78% when the drying temperature was 100°C, and 7.00% when the drying temperature was 150°C.

[0045] Example 10 A solubilized solution was obtained in the same manner as in Example 8, except that the drying time in drying step 1 was 60 minutes, the drying temperatures were 50°C, 100°C, and 150°C, and the pulverization step 2 was carried out for 180 minutes. The weight loss rate due to moisture loss in the biomass raw material was 3.72% when the drying temperature was 50°C, 6.58% when the drying temperature was 100°C, and 7.33% when the drying temperature was 150°C.

[0046] Example 11 A solubilized solution was obtained in the same manner as in Example 8, except that the drying time in drying step 1 was 3 hours, the drying temperature was 150°C, and the pulverization step 2 was carried out for 180 minutes. The weight loss rate due to moisture loss in the biomass raw material was 7.71%.

[0047] (Comparative Example) A solubilized solution was obtained in the same manner as in Example 1, except that the pulverization step 2 was carried out under heating at 150°C for 0, 180, 360, 540, and 720 minutes. w was calculated.

[0048] FIG. 4 shows the medium collision energy E per unit time for Examples 1 to 7. w 1 is a graph plotting the solubilization rate against the medium collision energy E per unit time. All solubilization rates are values ​​when the pulverization step 2 was carried out for 180 minutes. The solubilization rates of Examples 1 and 2 were 10% or less, while the solubilization rates of Examples 3 to 7 were 20% or more. w It was suggested that biomass materials can be efficiently solubilized if the flow rate is 3 J / s or more.

[0049] FIG. 5 is a graph plotting the solubilization rate against the grinding time for Examples 5 to 7 and the Comparative Example. It can be seen that in all of Examples 5 to 7, the solubilization rate increases as the grinding time increases. On the other hand, in the Comparative Example in which heat grinding was performed, the solubilization rate reached its maximum when the grinding time was about 360 minutes, and decreased when the grinding time exceeded 360 minutes. This is thought to be because lignin and the like were denatured and insolubilized by heating. Since no decrease in the solubilization rate was observed in Examples 5 to 7, it can be seen that the yield of water-soluble components does not fluctuate significantly even if grinding is performed for a certain period of time or longer. Furthermore, in Examples 5 to 7, the medium collision energy E per unit time w The larger the value, the higher the solubilization rate of the solubilized solution obtained in a shorter time.

[0050] 6 is a graph showing the solubilization rate versus the drying temperature in drying step 1 for Examples 8 to 11. Compared with Example 8, which did not undergo drying step 1, the solubilization rates of Examples 9 to 11 were higher, demonstrating that the solubilization rate can be increased by drying. It was also suggested that the solubilization rate can be increased as the drying temperature and drying time are longer.

[0051] In the above-described embodiment, the following configurations are envisioned. (1) A method for solubilizing a biomass raw material, comprising a crushing step 2 in which a biomass raw material containing cellulose and lignin is placed in a crushing chamber of a crusher and crushed without applying heat from the outside.

[0052] This configuration pulverizes biomass feedstock without applying external heat, thereby suppressing thermal denaturation of the mixture of oligosaccharides and lignin during the solubilization process. This allows for easy adjustment of the solubilization process time, since the yield of water-soluble components remains constant even when the pulverization process is continued for a certain period of time. Furthermore, since no heating is required, the pulverizer's configuration can be simplified.

[0053] (2) In the method for solubilizing a biomass raw material of (1), it is preferable that the temperature in the pulverization chamber in the pulverization step 2 is maintained in the range of 20°C or higher and 100°C or lower.

[0054] The temperature inside the milling chamber is likely to rise in the milling step 2. Therefore, by maintaining a constant temperature inside the milling chamber, it is possible to prevent the mixture of oligosaccharides and lignin from being denatured by heat and improve the yield of water-soluble components.

[0055] (3) The method for solubilizing a biomass raw material according to (1) or (2) further comprises a drying step 1 for drying the biomass raw material, and the drying step 1 is preferably carried out before the pulverization step 2.

[0056] According to this configuration, the moisture content of the biomass raw material can be reduced by the drying step 1, which suppresses the generation of water-insoluble components in the crushing step 2 and improves the yield of water-soluble components.

[0057] (4) In the method for solubilizing a biomass raw material of (3), the drying step 1 is preferably one in which the moisture content of the biomass raw material is reduced to 20% by mass or less.

[0058] According to this method, the production of water-insoluble components in the pulverization step 2 can be suppressed, and the yield of water-soluble components can be improved. [Industrial Applicability]

[0059] The present invention can be used in a method for solubilizing biomass materials containing cellulose and lignin. [Explanation of symbols]

[0060] 1: Drying process, 2: Crushing process

Claims

1. A method for solubilizing a biomass raw material, comprising a grinding step of grinding a biomass raw material containing cellulose and lignin that has been placed in a grinding chamber of a grinder without applying external heat.

2. 2. The method for solubilizing a biomass material according to claim 1, wherein the temperature inside the grinding chamber is maintained in a range of 20°C or higher and 100°C or lower during the grinding step.

3. Further comprising a drying step of drying the biomass material; The method for solubilizing a biomass material according to claim 1 or 2, wherein the drying step is carried out before the pulverization step.

4. The method for solubilizing a biomass material according to claim 3, wherein the drying step reduces the moisture content of the biomass material to 20% by mass or less.

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