Suspension

Abstract

To provide a suspension having high utilization efficiency of a pulverized material.SOLUTION: The average particle size of the pulverized material is 1 μm or more and 300 μm or less, and the viscosity at 20 °C. is 2mPa·s or more and 100mPa·s or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a suspension. [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 method for solubilizing a biomass raw material, in which a cellulose-containing biomass raw material is pulverized under heating at a temperature of 100°C or higher but lower than 300°C, and the water-soluble components are extracted with water. The biomass raw material is subjected to a mechanochemical effect by the heating and pulverization process, and is decomposed into components such as cellulose. The crystallinity of each component is further reduced and the molecular weight of each component is reduced, thereby generating water-soluble components. [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] The solubilization method for biomass raw materials described in Patent Document 1 includes a step of extracting water-soluble components from the pulverized material obtained by heating and pulverizing the biomass raw material with water. Therefore, when using the pulverized material, a step of extracting the water-soluble components is required, and the utilization efficiency of the pulverized material is not high.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a suspension that has high utilization efficiency of pulverized material. [Means for solving the problem]

[0007] The suspension according to the present invention is characterized in that it contains a pulverized material obtained from a biomass raw material containing cellulose and water, and that the pulverized material has an average particle size of 1 μm or more and 300 μm or less, and a viscosity at 20°C of 2 mPa·s or more and 100 mPa·s or less.

[0008] According to this configuration, by suspending the pulverized material in water, it is possible to dissolve the water-soluble components contained in the pulverized material in the suspension, thereby eliminating the need for a process for extracting the water-soluble components when using the pulverized material. Furthermore, since the suspension can be used directly in other processes, it is possible to improve the utilization efficiency of the pulverized material. Furthermore, since the average particle size of the pulverized material is 1 μm or more and 300 μm or less, the pulverized material is easily suspended in water, making it easy to dissolve the water-soluble components in the suspension. Furthermore, since the viscosity at 20°C is 2 mPa·s or more and 100 mPa·s or less, the viscosity of the suspension is relatively low, making it easy to transport and handle. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a graph showing the average particle diameters of pulverized materials according to Examples and Comparative Examples. [Figure 2] FIG. 10 is a diagram showing the viscosity of suspensions according to the examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the suspension 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] The suspension according to the present invention contains water and a pulverized material obtained by mechanochemically treating a biomass raw material containing cellulose.

[0012] In addition to cellulose, the biomass feedstock of the present invention may contain oligosaccharides and polysaccharides such as lignin, starch, hemicellulose, and pectin. Examples of biomass feedstocks include grass or plant biomass such as rice straw, wheat straw, and bagasse; thinning materials such as bamboo and bamboo grass; wood processing waste such as sawdust, chips, and scraps; woody biomass such as roadside tree pruning materials, wooden building waste, bark, and driftwood; and cellulose products such as waste paper. Furthermore, 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 feedstocks. These biomass feedstocks may be used alone or in combination with different types.

[0013] Mechanochemical processing refers to a process in which a material is subjected to mechanical stress, such as pulverization, to physically or chemically change it. Mechanochemical processing is carried out by applying mechanical stress to biomass raw materials using, for example, a ball mill such as a planetary ball mill, or a grinder or disperser with a grinding medium, such as a rod mill or a vibratory mill. Through mechanochemical processing, biomass raw materials are decomposed into components such as cellulose and lignin, and the crystallinity of these components is reduced and the resulting particles are decomposed into smaller molecules, resulting in a pulverized material containing water-soluble components. Compared to solubilization processes using chemicals such as sulfuric acid, mechanochemical processing of biomass raw materials is safer and less environmentally hazardous in terms of production process.

[0014] The mechanochemical treatment according to the present invention may be carried out under any conditions, for example, the biomass raw material may be pulverized at a temperature ranging from room temperature to 300°C. When the biomass raw material is heated and pulverized, the heating method is not particularly limited, and the container may be heated using an electric heater, high frequency waves, microwaves, steam, or the like. The pulverization treatment is preferably carried out for 10 minutes or more. Since the longer the treatment time, the more the reaction of depolymerization progresses, it is desirable to carry out the treatment for a long period of time, but in order to efficiently obtain water-soluble components, it is preferable to carry out the treatment for about 10 minutes to 2 hours.

[0015] The rotation speed of the ball mill in the mechanochemical treatment is preferably in the range of 200 rpm to 2000 rpm. The higher the rotation speed, the more rapidly carbonization progresses, but a rotation speed of more than 300 rpm and less than 1500 rpm is preferred in consideration of the balance between production energy and equipment load. The ball diameter and ball weight can be set to any value, but in order to pulverize the biomass raw material to 10 mm or less, if the ball mill vessel capacity is 2 L, it is recommended that they be 1 mmφ to 30 mmφ and 1 kg to 8 kg.

[0016] The biomass raw material may be coarsely pulverized before undergoing mechanochemical treatment. In the coarse pulverization, the biomass raw material may be pulverized into an easily handleable shape, for example, about 0.5 mm to 100 mm. For the coarse pulverization, 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.

[0017] Furthermore, the biomass raw material or coarsely pulverized biomass raw material may be dried before undergoing mechanochemical treatment. This is because dry pulverization of biomass raw material with a low moisture content can efficiently reduce the crystallinity of cellulose and lignin. The moisture content of the biomass raw material may be measured and the decision as to whether or not to dry the biomass raw material may be made based on the moisture content. The moisture content of the biomass raw material to be subjected to mechanochemical treatment may be 20% by mass or less, more preferably 10% by mass or less. The moisture content of the biomass raw 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 may be performed by natural drying, or by heating the biomass raw material with hot air drying, an electric heater, or the like.

[0018] The average particle size of the pulverized material obtained by mechanochemical treatment should be 1 μm or more and 300 μm or less. This average particle size is the particle size (D50) at which the cumulative weight percentage is 50% in the particle size distribution obtained by laser diffraction / scattering. If the average particle size of the pulverized material is 300 μm or less, the pulverized material can be easily suspended in water, making it easier to dissolve the water-soluble components contained in the pulverized material in water. Furthermore, if the average particle size of the pulverized material is 1 μm or more, the energy required for mechanochemical treatment can be reduced, making it more economical.

[0019] Furthermore, the ratio of the amount of carbon contained in the water-soluble components to the amount of carbon contained in sugars such as cellulose, hemicellulose, and oligosaccharides contained in the biomass feedstock (amount of water-soluble organic carbon / amount of carbon contained in the sugars contained in the feedstock; also referred to as the solubilization rate) can be any value, but from the perspective of efficient production and use of the suspension, it is desirable for it to be 10% or higher. If the solubilization rate is 10% or higher, the concentration of the water-soluble components in the suspension can be increased, thereby improving the utilization efficiency of the suspension.

[0020] The pulverized material obtained by mechanochemical treatment is suspended in water to obtain a suspension. The mass content of the pulverized material in the suspension can be any value, but is preferably 0.3% to 30%. A mass content of 0.3% or more allows the water-soluble components contained in the pulverized material to dissolve in the suspension, making it easier to use the suspension in the next step. A mass content of 30% or less reduces the viscosity of the suspension, improving its handleability. Furthermore, by suspending the pulverized material in water and dissolving the water-soluble components into the suspension, the process of extracting the water-soluble components with water can be omitted, thereby improving the utilization efficiency of the pulverized material. The mass content of the pulverized material in the suspension may be varied depending on the solubilization rate of the pulverized material or on the various conditions of the mechanochemical treatment.

[0021] The viscosity of the suspension in the present invention, as measured using an E-type viscometer at a temperature of 20°C and a rotation speed of 250 rpm, is preferably 2 mPa·s or more and 100 mPa·s or less. If the viscosity of the suspension is within the above range, the suspension can be easily transported and its handling can be improved. The viscosity of the suspension is more preferably 2 mPa·s or more and 50 mPa·s, and even more preferably 3 mPa·s or more and 10 mPa·s. Viscosity measurements may also be performed using the supernatant obtained by centrifuging the suspension.

[0022] [Method for producing suspension] Next, a method for producing a suspension according to the present invention will be described. The method for producing a suspension includes a treatment step of mechanochemically treating a biomass raw material, and a suspending step of suspending the pulverized material obtained by the treatment step in water.

[0023] First, in the treatment step, a mechanical stress is applied to the biomass raw material using a grinder with grinding media such as a ball mill, thereby performing mechanochemical treatment. To improve the processing efficiency of the biomass raw material, the biomass raw material may be coarsely ground prior to the treatment step, or may be dried to a predetermined moisture content. The treatment step may be performed at room temperature or under heating. By varying various conditions of the mechanochemical treatment, such as the grinding time and the grinder rotation speed, a desired mechanical stress is applied to the biomass raw material, thereby obtaining a ground product with a desired solubilization rate.

[0024] Subsequently, a suspending step is performed to obtain a suspension in which the pulverized material is dispersed in water. In the suspending step, the pulverized material is preferably suspended in water so that the mass content of the pulverized material in the suspension is 0.3% to 30%. The pulverized material content may be varied depending on the solubilization rate of the pulverized material and various conditions of the mechanochemical treatment. The suspending step can be performed, for example, by stirring the pulverized material and water at a predetermined rotation speed. The suspending step may be performed by adding water to the pulverized material, or by adding the pulverized material to water. The temperature of the water in the suspending step can be set to any value.

[0025] [Example] Examples of the present invention will be described below, but the present invention is not limited to the descriptions of these examples.

[0026] (Example) A pulverized material was prepared using biomass raw material with a sugar content of 66.8%, other components of 28.6%, and a moisture content of 4.6%. The sugar content of the biomass raw material was calculated by sugar composition analysis. The biomass raw material was first coarsely pulverized using a cutting mill to pass through a 1 mm pore screen, and then pulverized using a heater-equipped ball mill at a temperature of 120°C, a rotation speed of 700 rpm, and for a pulverization time of 10, 47, 62, 92, or 107 minutes. The pulverized material was then suspended in water to a mass content of 15% to obtain a suspension.

[0027] (Comparative Example) A suspension was obtained in the same manner as in Example 1, except that the coarsely pulverized material was suspended in water instead of the pulverized material.

[0028] The average particle size of each of the pulverized materials according to the Examples and Comparative Examples was determined by a laser diffraction / scattering method. Figure 1 is a graph plotting the average particle size against the pulverization time of the biomass raw material. As shown in Figure 1, the coarsely pulverized material used in the Comparative Examples had an average particle size of approximately 500 μm, while the average particle size of the pulverized material according to the Examples was 20 μm to 48 μm. The suspension according to the Examples was in a slurry state when observed with the naked eye, whereas the suspension according to the Comparative Examples was in a liquid state in which the coarsely pulverized material could be visually confirmed. This suggests that the smaller the average particle size, the easier it is for the pulverized material to be suspended in water and the handleability of the suspension can be improved.

[0029] Figure 2 shows the viscosity measurement results for a suspension according to an example where the grinding time was 87 minutes. The viscosity was measured using the supernatant obtained by centrifuging the suspension at 10,000 x g and 15°C for 10 minutes. The measurement was carried out using an E-type viscometer at a rotation speed of 250 rpm and temperatures of 4°C, 20°C, and 40°C. At all temperatures, the viscosity was 2 mPa·s or more and 100 mPa·s or less. The suspension was in a slurry state and was easy to handle.

[0030] In the above-described embodiment, the following configurations are envisioned. (1) A suspension containing a pulverized material obtained from a biomass raw material containing cellulose and water, wherein the pulverized material has an average particle size of 1 μm or more and 300 μm or less, and a viscosity at 20°C of 2 mPa·s or more and 100 mPa·s or less.

[0031] According to this configuration, by suspending the pulverized material in water, it is possible to dissolve the water-soluble components contained in the pulverized material in the suspension, thereby eliminating the need for a process for extracting the water-soluble components when using the pulverized material. Furthermore, since the suspension can be used directly in other processes, it is possible to improve the utilization efficiency of the pulverized material. Furthermore, since the average particle size of the pulverized material is 1 μm or more and 300 μm or less, the pulverized material is easily suspended in water, making it easy to dissolve the water-soluble components in the suspension. Furthermore, since the viscosity at 20°C is 2 mPa·s or more and 100 mPa·s or less, the viscosity of the suspension is relatively low, making it easy to transport and handle.

[0032] In the suspension of (2)(1), it is preferable that the content of the pulverized material by mass is 0.3% or more and 30% or less.

[0033] According to this configuration, the viscosity of the suspension can be maintained within a certain range, which makes it possible to improve the handling properties of the suspension.

[0034] (3) In the suspension of (1) or (2), the pulverized material is preferably a biomass raw material that has been subjected to mechanochemical treatment.

[0035] According to this method, cellulose and other components contained in biomass raw materials can be converted into water-soluble components and dissolved in a suspension, enabling the effective use of biomass raw materials. Furthermore, since water-soluble components can be obtained from biomass raw materials without using chemicals, the manufacturing process is safe and has a low environmental impact. [Industrial Applicability]

[0036] The present invention can be used for a suspension containing a ground material and water.

Claims

1. A suspension comprising a pulverized material obtained from a biomass raw material containing cellulose and water, The average particle size of the pulverized product is 1 μm or more and 300 μm or less, A suspension having a viscosity at 20°C of 2 mPa·s or more and 100 mPa·s or less.

2. 2. The suspension according to claim 1, wherein the content of the pulverized material by mass is 0.3% or more and 30% or less.

3. The suspension according to claim 1 or 2, wherein the pulverized material is obtained by mechanochemically treating the biomass raw material.

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