Method for producing lignin-containing powder

Abstract

This invention provides a method for producing a powder with a high lignin content and smaller particle size from the saccharification and fermentation residue of lignocellulosic biomass. [Solution] A method for producing lignin-containing powder, comprising filtering a residue or solution containing lignin generated during the process of saccharifying or fermenting lignocellulosic biomass in a wet state using a filter filtration method, separating the obtained filtrate into solid and liquid components, drying the obtained solid residue, and grinding the obtained dried material to produce a lignin-containing powder, wherein the filtration is performed using a filter with a mesh opening of 105 μm to 1000 μm.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a lignin-containing powder from the saccharification and fermentation residue of lignocellulosic biomass. [Background technology]

[0002] As one of the recent efforts toward realizing a society that does not rely on fossil fuels, the development of biomass utilization technologies is progressing. While the production of bioethanol using sugarcane, corn, and other raw materials is expanding, the development of non-edible biomass utilization technologies is also progressing with the aim of avoiding competition with food production and making effective use of limited resources. Non-edible biomass mainly consists of plant biomass (lignocellulosic biomass) composed of three components: cellulose, hemicellulose, and lignin. These three components are twisted together into fibers at the molecular level, and these are further layered to form strong plant cell walls, which make up the stems and leaves of the plant itself.

[0003] Ethanol production using lignocellulosic biomass as a raw material consists of a pretreatment step in which the biomass raw material is pretreated thermochemically, a saccharification step in which the biomass after the pretreatment step is enzymatically treated to produce a saccharified liquid, a fermentation step in which a microbial culture solution is added to the saccharified liquid obtained in the saccharification step to carry out ethanol fermentation, and a purification step in which ethanol is separated from the fermented liquid obtained in the fermentation step by distillation or the like. By selectively decomposing and saccharifying cellulose and hemicellulose in the biomass raw material to produce monosaccharides in high yield, economical ethanol production with high yield becomes possible.

[0004] In ethanol production, a problem arises because lignin in the biomass raw material remains as a solid, resulting in the generation of a large amount of fermentation residue. On the other hand, since lignin can be decomposed to yield phenol derivatives and other substances, it can be used as a raw material for chemical industrial products such as resins, composite materials, and surfactants. Therefore, the development of technologies to utilize saccharification and fermentation residue discharged from cellulose ethanol production processes as a chemical raw material is progressing, and related patents can be found. Saccharification and fermentation residue discharged from cellulose ethanol production processes is expected to be a promising raw material resource for many chemical manufacturing processes that use lignin as the main raw material because it tends to contain lignin in high purity, yields lignin with a low degree of modification through a gradual biomass decomposition process, and can be supplied cheaply and stably as a residue for industrial use such as ethanol production residue.

[0005] Cellulose, hemicellulose, and lignin all have different chemical structures and properties. Therefore, when using them as substitutes for chemical product raw materials, it is necessary to recover the desired components with high purity and high yield. For example, in the aforementioned method that utilizes one or two of the three components, the remaining components cannot be effectively utilized, resulting in a low yield per unit biomass and thus increasing costs. In order to construct an economically rational process for the effective utilization of lignocellulosic biomass, the development of technologies for the effective utilization of by-product residue components is also a challenge.

[0006] For example, Patent Document 1 discloses an invention relating to a system for recovering organic solvent-soluble lignin from the residue generated in the process of producing bioethanol from cellulose and hemicellulose in lignocellulosic biomass. Patent Document 2 discloses an invention relating to a rubber composition for studless tires that improves ice performance by incorporating water-insoluble lignin extracted from fermentation residue. Furthermore, it is possible to selectively liquefy and extract lignin by selectively chemically modifying it with sulfonic acid groups, phenolic groups, PEG groups, etc., and changing its solubility. Patent Document 3 discloses an invention relating to a method for separating lignin in high yield as modified lignin by reacting phenolic compounds with fermentation residue in ethanol production. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2021-42289 [Patent Document 2] Japanese Patent Publication No. 2023-10563 [Patent Document 3] Japanese Patent Publication No. 2023-24831 [Overview of the project] [Problems that the invention aims to solve]

[0008] When using saccharification and fermentation residues as raw materials for chemical products, it is desirable that their quality be stable. However, lignocellulosic biomass is a naturally derived material, and its composition varies depending on the plant species and part of the plant. In addition, it is affected by factors such as spoilage and poor growth, so its composition is not always stable. These effects also affect saccharification and fermentation performance, and even saccharification and fermentation residues produced as by-products under the same process and production conditions cannot have a uniform composition. Due to the uncertainty of the biomass composition itself, as well as the characteristics of the manufacturing process, it is difficult to achieve a process that decomposes and saccharifies 100% of cellulose and hemicellulose, and saccharification and fermentation residues always contain impurities other than lignin, such as cellulose and hemicellulose.

[0009] The present invention has been made in view of the above circumstances, and provides a method for producing a powder with a high lignin content and smaller particle size from the saccharification and fermentation residue of lignocellulosic biomass. [Means for solving the problem]

[0010] In other words, the present invention includes the following embodiments. (1) A residue containing lignin, or a solution containing the residue, generated in the process of saccharifying or fermenting lignocellulosic biomass, is filtered in a wet state by filter filtration, the resulting filtrate is subjected to solid-liquid separation, the resulting solid residue is dried, and the resulting dried material is pulverized to produce a powder containing lignin. A method for producing lignin-containing powder, wherein the filtration is performed using a filter with a mesh opening of 105 μm to 1000 μm. (2) A method for producing the lignin-containing powder according to (1), wherein the mesh opening of the filter is 170 μm to 500 μm. (3) The method for producing the lignin-containing powder according to (1) or (2), wherein in the filtration, at least a portion of the deposits on the surface of the filter is removed once or more times. (4) The filtration is performed using a filter filtration device equipped with a mechanism to prevent clogging of the filter, The clogging suppression mechanism is a scraping mechanism configured to continuously or intermittently scrape off the deposits on the surface of the filter, or a vibration mechanism configured to continuously or intermittently vibrate the filter. The method for producing the lignin-containing powder according to any one of (1) to (3) above. (5) The method for producing a lignin-containing powder according to any one of (1) to (4) above, wherein the residue or solution is a saccharified liquid, a fermentation liquid, a distillation effluent generated in the process of saccharifying or fermenting lignocellulosic biomass, or a residue obtained by solid-liquid separation from these. (6) The method for producing a lignin-containing powder according to any one of (1) to (5) above, wherein the pulverization is performed by first coarsely pulverizing the dried product and then further finely pulverizing the obtained coarsely pulverized product. (7) Regarding the D of the powder 90 The method for producing a lignin-containing powder according to any one of (1) to (6) above, which is 212.0 μm or less. (8) Regarding the D of the powder 90 The method for producing a lignin-containing powder according to any one of (1) to (7) above, which is 107.8 μm or less. (9) Regarding the D of the powder 90 The method for producing a lignin-containing powder according to any one of (1) to (8) above, which is 88.2 μm or less. (10) Using a residue containing lignin generated in the process of saccharifying or fermenting lignocellulosic biomass or a solution containing the same as a raw material, and D 90 A lignin-containing powder having a particle size of 88.2 μm or less.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a method for producing a lignin-containing powder having a high lignin content and a small particle size from a saccharification / fermentation residue of lignocellulosic biomass or a solution containing the same.

Brief Description of the Drawings

[0012] [Figure 1]In Example 2, it is a two-dimensional plot of the circularity and equivalent circle diameter of particles in the fraction below 1000 μm and above 512 μm (Fig. 1(A)) and particles in the fraction below 276 μm (Fig. 1(B)). [Figure 2] In Example 2, it is a photograph of particles in the fraction below 1000 μm and above 512 μm (Fig. 1(A)) and particles in the fraction below 276 μm (Fig. 1(B)).

Modes for Carrying Out the Invention

[0013] Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an exemplification for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be appropriately modified and implemented within the scope of its gist.

[0014] In the present invention and the present specification, examples of the "lignocellulosic biomass" include woody plants (also referred to as woody biomass), herbaceous plants (also referred to as herbaceous biomass), processed products thereof, and wastes thereof. Examples of the woody plants include, for example, cedar, cypress, larch, pine, rice pine, rice cedar, rice hemlock, poplar, birch, willow, eucalyptus, kunugi, konara, oak, elm, beech, acacia, bamboo, sasaya, oil palm, sago palm, etc. Examples of the herbaceous plants include, for example, bamboo, palm; gramineous plants such as rice (including rice straw), wheat (including wheat straw), sugarcane (including bagasse), reed, miscanthus, corn (including corn stover, corn cob, corn hull), sorghum (including sweet sorghum), switchgrass, erianthus, napier grass; jatropha, cashew, etc.

[0015] The lignocellulosic biomass also includes barks, branches, inflorescences, fruit husks, etc. of the above-mentioned woody plants. Further, it includes processed materials such as plywood, fiberboard, and laminated wood using the above-mentioned woody plants, and members disassembled after use in buildings. Also, processed products of lignocellulosic biomass such as paper and waste paper are included in the lignocellulosic biomass.

[0016] Lignin is a natural polymer that is one of the three main components of lignocellulosic biomass. For example, bagasse, a type of herbaceous biomass, contains 5% to 30% lignin by mass.

[0017] Lignin's basic skeleton is composed of an aromatic nucleus (benzene ring), and based on its structure, it is classified into G rings, S rings, and H rings. A G ring has one methoxy group (-OCH3) at the ortho position of the phenol skeleton, an S ring has two methoxy groups at the ortho position, and an H ring does not have a methoxy group at the ortho position. Lignin in herbaceous biomass such as bagasse contains all three basic skeletons: H rings, G rings, and S rings. Among lignin derived from woody biomass, lignin from coniferous trees has a G ring as its basic skeleton, while lignin from broad-leaved trees has both G and S rings as its basic skeleton.

[0018] Cellulose contains hexoses, which are composed of six carbon atoms. Therefore, when cellulose undergoes hydrolysis, it produces monosaccharides (such as glucose) made up of six carbon atoms, and oligosaccharides (such as cellobiose) made up of multiple hexose monosaccharides linked together.

[0019] "Hemicellulose" includes complex polysaccharides such as glucomannan and glucuronoxylan, which are composed of pentoses (C5 sugars) with five carbon atoms as constituent units, such as xylose, and hexoses (C6 sugars) with six carbon atoms as constituent units, such as mannose, arabinose, and 4-O-methylglucuronic acid. Therefore, when hemicellulose undergoes hydrolysis, it produces pentose monosaccharides with five carbon atoms, pentose oligosaccharides in which multiple pentose monosaccharides are linked together, hexose monosaccharides with six carbon atoms, hexose oligosaccharides in which multiple hexose monosaccharides are linked together, and oligosaccharides in which multiple pentose monosaccharides and hexose monosaccharides are linked together.

[0020] <Method for producing lignin-containing powder> The method for producing lignin-containing powder according to this embodiment (hereinafter sometimes abbreviated as "the method for producing this embodiment") is a method for producing lignin-containing powder from a lignin-containing residue or a solution containing the residue generated in the process of saccharifying or fermenting lignocellulosic biomass. Specifically, the residue to be used as raw material is filtered by a filter filtration method in a wet state, the obtained filtrate is subjected to solid-liquid separation, the obtained solid residue is dried, and the obtained dried material is pulverized to produce lignin-containing powder.

[0021] The residue used as a raw material in the manufacturing method of this embodiment is a lignin-containing residue generated during the process of saccharification or fermentation of lignocellulosic biomass (hereinafter sometimes referred to as "saccharification / fermentation residue of lignocellulosic biomass" or simply abbreviated as "saccharification / fermentation residue"). Saccharification or fermentation consumes cellulose and hemicellulose in the lignocellulosic biomass. In other words, the saccharification / fermentation residue of lignocellulosic biomass is a residue in which at least a portion of the cellulose and hemicellulose has been decomposed and consumed.

[0022] Directly pulverizing plant-based biomass or woody biomass requires a large amount of energy. In the manufacturing method of this embodiment, by using saccharification and fermentation residue as a raw material, a powder containing lignin, which is suitable as a raw material for chemical products, can be efficiently produced with less energy.

[0023] Saccharification and fermentation residues always contain undecomposed biomass in addition to the biomass decomposed by saccharification and fermentation. Saccharification and fermentation residues mixed with this undecomposed biomass are less efficient to pulverize, require longer pulverization times, and demand more crushing power. In the manufacturing method of this embodiment, the undecomposed biomass is efficiently removed by filtering the raw material saccharification and fermentation residue in a wet state using a filter with a specific mesh size. As a result, lignin-containing powders can be produced with unprecedented energy efficiency.

[0024] Examples of saccharification / fermentation residues or solutions containing the same used in the manufacturing method of this embodiment include residues or solutions containing the same generated in the process of decomposing and saccharifying cellulose and hemicellulose in lignocellulosic biomass to produce sugars and fermentation products. Specifically, as raw materials in the manufacturing method of this embodiment, residues or solutions containing the same generated in the process of producing biochemicals using lignocellulosic biomass as a raw material can be used. Examples of such biochemicals include alcohols such as bioethanol, biobutanol, and propanediol, amino acids, and organic acids such as citric acid, lactic acid, and succinic acid. Preferably, the saccharification / fermentation residues or solutions containing the same used as raw materials in the manufacturing method of this embodiment are saccharified liquid, fermented liquid, distillation wastewater, or residues obtained by solid-liquid separation from these generated in the process of producing bioethanol using lignocellulosic biomass as a raw material. Particularly preferred are saccharification residues remaining after pretreatment of lignocellulosic biomass by dilute sulfuric acid pulping and further decomposition of the obtained pretreated raw materials by enzymatic saccharification.

[0025] During saccharification and fermentation, cellulose and hemicellulose in lignocellulosic biomass are broken down, and their cell wall and fibrous structures are pulverized. Therefore, the saccharification and fermentation residue of lignocellulosic biomass mainly contains cellulose and hemicellulose that were not fully saccharified, lignin that has been broken down into fine particles due to the pulverization of cell wall structures, and undecomposed biomass containing plant cell walls and fibrous structures. In addition, it may also contain foreign matter originating from the raw material (lignocellulosic biomass) or the manufacturing process. If the saccharification and fermentation residue is dried and then pulverized, these components other than lignin are also incorporated into the powder, resulting in a low lignin content. Furthermore, lignin in the saccharification and fermentation residue tends to adhere to the fibrous undecomposed biomass during drying, forming aggregates with large apparent particle sizes. Since undecomposed biomass is difficult to break down through physical pulverization, the powder obtained by pulverizing the dried saccharification and fermentation residue tends to have a high proportion of large particles. While large particles in the resulting powder can be removed using dry sieving or similar methods, this process also removes lignin that is agglomerated with foreign matter and undecomposed biomass, thus reducing the efficiency of lignin recovery.

[0026] Examples of saccharification and fermentation residues used in the manufacturing method of this embodiment include residues obtained after saccharification treatment following pretreatment of lignocellulosic biomass, and residues obtained after fermentation treatment following saccharification treatment. The conditions for pretreatment, saccharification treatment, and fermentation treatment are not particularly limited.

[0027] For example, pretreatment can be carried out by dilute sulfuric acid pulping. Dilute sulfuric acid pulping is a method of heating and pressurizing in the presence of dilute sulfuric acid. The dilute sulfuric acid used can be added, for example, so that the pH of the pretreatment solution containing lignocellulosic biomass is between 0.8 and 6.7. By performing the pretreatment step, the lignocellulosic biomass can be moderately decomposed, allowing the saccharification reaction to be carried out efficiently in the subsequent saccharification treatment.

[0028] The intensity of the pretreatment, that is, the intensity of the decomposition of lignin, cellulose, and hemicellulose, can be controlled by three parameters: temperature, time, and pH. Therefore, the treatment intensity can be evaluated using the Combined Severity Index (CSI), expressed by equation (I) below, with the above three parameters as variables. A higher CSI value tends to indicate a higher biomass decomposition intensity, while a lower CSI value tends to indicate a lower biomass decomposition intensity. By setting the pretreatment conditions so that the CSI calculated from equation (I) falls within a predetermined range, the desired decomposition intensity can be achieved.

[0029]

number

[0030] (In equation (I), X is time, Y is temperature, and Z is pH.)

[0031] The higher the biomass decomposition strength, i.e., the larger the CSI value, the more likely it is that a residue containing a large amount of organic solvent-soluble lignin will be obtained. For this reason, the pretreatment of the saccharification and fermentation residue used in the production method of this embodiment is preferably carried out under conditions where the CSI is 1.0 or more and 3.0 or less, more preferably 1.2 or more and 2.8 or less, even more preferably 1.5 or more and 2.7 or less, and particularly preferably 1.5 or more and 2.5 or less. A CSI of 1.5 or more than the lower limit can further improve the amount of organic solvent-soluble lignin produced in the pretreatment and further improve the enzymatic saccharification rate of C5 sugars and C6 sugars. On the other hand, a CSI of 1.5 or less than the upper limit can more effectively suppress the production of furfural due to the over-decomposition of xylose and more effectively suppress the decrease in the enzymatic saccharification rate of C5 sugars and C6 sugars.

[0032] In the pretreatment process, the specific treatment conditions that fall within the above CSI range include a pH of 0.8 or more and less than 1.5, 0.8 or more and 1.4 or less, and 0.8 or more and 1.2 or less.

[0033] The processing temperature can be, for example, between 100°C and 250°C, between 120°C and 200°C, or between 150°C and 180°C.

[0034] The processing time can be, for example, between 3 minutes and 150 minutes, between 5 minutes and 120 minutes, between 7 minutes and 90 minutes, or between 8 minutes and 40 minutes.

[0035] The reaction vessel used in the dilute sulfuric acid pulping method is not particularly limited as long as it is a steam-supplied type, but it is conceivable to process it in a device that has an acid-resistant heating and pressure device such as an autoclave, or an acid-resistant heating and pressure vessel, and further incorporates a screw feeder to enable continuous processing.

[0036] In the pretreatment process, the biomass may be crushed using a mill or the like before or after treatment by dilute sulfuric acid pulverization.

[0037] The saccharification treatment after pretreatment is carried out using enzymes with cellulose and hemicellulose contained in the pretreated lignocellulosic biomass as substrates. The enzymes referred to here are mainly saccharifying enzymes. Examples of saccharifying enzymes include cellulase, which breaks down cellulose; hemicellulase, which breaks down hemicellulose; and amylase, which breaks down starch.

[0038] The cellulase can be any enzyme that breaks down cellulose into monosaccharides or oligosaccharides such as glucose. Examples include enzymes having at least one of the activities of endoglucanase (EG), cellobiohydrolase (CBH), and β-glucosidase (BGL). From the viewpoint of enzyme activity, a mixture of enzymes having these activities is preferable.

[0039] The hemicellulase mentioned above can be any enzyme that breaks down hemicellulose into monosaccharides or oligosaccharides such as xylose. Examples include those having at least one of the activities of xylanase, xylosidase, mannanase, galactosidase, glucuronidase, and arabinofuranosidase. From the viewpoint of enzyme activity, a mixture of enzymes having each of these activities is preferable.

[0040] The origin of these saccharifying enzymes, such as cellulases and hemicellulases, is not limited. For example, saccharifying enzymes such as cellulases and hemicellulases derived from microorganisms of the genera Trichoderma, Acremonium, Aspergillus, Bacillus, Pseudomonas, Penicillium, Aeromonas, Irpex, Sporotrichum, and Humicola can be used.

[0041] The saccharification temperature is preferably between 45°C and 70°C, more preferably between 45°C and 55°C, and particularly preferably 50°C. The saccharification time is preferably between 12 hours and 120 hours, and more preferably between 24 hours and 96 hours.

[0042] The saccharification process is not particularly limited and can be carried out using known saccharification apparatus. Specifically, examples of saccharification apparatus include agitation type, aeration agitation type, bubble tower type, fluidized bed type, and packed bed type. In addition, the saccharification apparatus may be equipped with a temperature control device such as a hot water circulating jacket on the outside of the apparatus to maintain a constant temperature inside the apparatus.

[0043] The fermentation process involves adding the saccharified liquid obtained from the saccharification process, the saccharification residue on which saccharifying enzymes have been adsorbed, and microorganisms, and stirring the mixture. The saccharification residue contains unsaccharified polysaccharides such as cellulose and hemicellulose, as well as saccharifying enzymes adsorbed onto the residue. Therefore, by using both the saccharified liquid and the saccharification residue obtained from the saccharification process during the fermentation process, the saccharification reaction can be carried out simultaneously during the fermentation reaction, generating monosaccharides and oligosaccharides that serve as substrates for microbial fermentation.

[0044] The fermentation conditions can be carried out appropriately based on conventional technology. For example, the fermentation temperature is preferably 25°C to 50°C, more preferably 28°C to 35°C, and particularly preferably 32°C. The fermentation time is preferably 24 hours to 120 hours, more preferably 24 hours to 96 hours, and even more preferably 24 hours to 72 hours.

[0045] There are no specific limitations on the microorganisms used, as long as they can produce the target lignocellulosic biomass-derived compound. Specifically, examples include yeast and bacteria, and genetically modified microorganisms are also preferably used.

[0046] In the manufacturing method of this embodiment, the saccharification and fermentation residue is filtered while still wet. When the saccharification and fermentation residue is dried, the lignin particles aggregate during drying, resulting in a particle size larger than that of the undecomposed biomass. Even if the dried material after such large particle size formation is crushed and sieved, the finely divided lignin particles become entangled with the larger particles due to electrostatic aggregation, etc., and the yield of finely divided lignin by filter filtration is significantly reduced. In the manufacturing method of this embodiment, by filtering the residue obtained in the saccharification and fermentation process without drying, foreign matter and undecomposed biomass can be removed without significantly reducing the lignin recovery rate. In particular, undecomposed biomass often takes the form of a fibrous, high aspect ratio-like shape and is widely distributed in terms of major diameter from a few millimeters to several hundred micrometers, so a filter with a mesh structure can efficiently remove undecomposed biomass with a long major diameter. In the manufacturing method of this embodiment, by using a filter with a mesh opening of 105 μm to 1000 μm, it is possible to selectively remove undecomposed biomass while recovering the finely particulated lignin.

[0047] In the manufacturing method of this embodiment, the saccharification and fermentation residue subjected to filter filtration is preferably the residue before the moisture removal treatment, not just the drying treatment. For example, when using the solid content in the distillation wastewater after ethanol distillation separation obtained in the cellulose ethanol manufacturing process as the raw material for saccharification and fermentation residue, the saccharification and fermentation residue recovered by decanting the distillation wastewater by centrifugal separation may be used as the raw material for filter filtration, but it is preferable to use the distillation wastewater as is for filter filtration.

[0048] By making the mesh opening of the filter used for filtration sufficiently small, foreign matter and undecomposed biomass can be removed more efficiently. On the other hand, since saccharification and fermentation residues contain many different solid components, clogging is likely to occur if the mesh opening is small. In the manufacturing method of this embodiment, the mesh opening of the filter used for filtration is not particularly limited as long as it is within the range of 105 μm to 1000 μm, but it is preferable that it be within the range of 105 μm to 500 μm, more preferably within the range of 170 μm to 500 μm, and even more preferably within the range of 177 μm to 500 μm, in order to be excellent in both the separation performance of lignin from other components such as undecomposed biomass and the separation and recovery efficiency of filtration (resistance to clogging). By setting the mesh opening of the filter used for filtration to 500 μm or less, it is possible to produce a powder suitable as a raw material for chemical products, which has high circularity, a small aspect ratio, and a large proportion of particles with small particle size.

[0049] The saccharification and fermentation residue of lignocellulosic biomass contains a large amount of fibrous material, including undecomposed biomass. As a result, longer fibrous undecomposed biomass and other materials collected on the filter surface act as nuclei, trapping finer fibers, ultimately forming a muddy self-film on the filter surface. This clogging caused by self-film formation leads to even fine lignin particles being collected on the filter surface, significantly reducing the lignin recovery rate. Therefore, in the manufacturing method of this embodiment, it is preferable to perform a process to remove at least a portion of the deposits on the filter surface at least once during the filter filtration. Removing the deposits from the filter surface eliminates filter clogging. The method for removing the deposits is not particularly limited and may be done manually or using a filter filtration device equipped with a filter clogging suppression mechanism.

[0050] Examples of mechanisms for preventing filter clogging include a scraping mechanism configured to continuously or intermittently scrape off deposits from the filter surface, and a vibration mechanism configured to continuously or intermittently vibrate the filter. The filter filtration device equipped with a clogging prevention mechanism used in the manufacturing method of this embodiment may be a device equipped with either a scraping mechanism or a vibration mechanism, or a device equipped with both a scraping mechanism and a vibration mechanism. The scraping mechanism may be any structure that can remove deposits from the filter surface by scraping it, such as a scraper. The scraper may be blade-shaped (also called knife-shaped or blade-shaped) or spatula-shaped. The vibration mechanism may be a mechanism that vibrates the entire filter, or it may vibrate each of the linear structures that make up the filter mesh. Specific examples of vibration mechanisms include a continuous belt filter, a vibrating screen, an ultrasonic vibrating screen, etc. In addition, a continuous moving filter mechanism can also be used. The mechanism in question is one in which the filter itself is continuously refreshed by continuously or intermittently replacing the filter, and the filter itself carries the cake (saccharification and fermentation residue subjected to filter filtration), so that the cake does not continue to accumulate in the filter. For example, it is a mechanism in which the filtered part (active) and the unfiltered part (inactive) are continuously replaced in a belt-like manner, and the cake is scraped out when filtration is not performed.

[0051] Next, the filtrate obtained by filter filtration is subjected to solid-liquid separation, and the resulting solid residue is dried. The resulting dried material is then pulverized to produce a powder containing lignin. Because undifferentiated bagasse and large foreign matter are removed by the filter filtration, the lignin content of the filtrate is higher than that of the saccharification and fermentation residue used as raw material. By using this, a powder with a high lignin content can be produced.

[0052] The solid-liquid separation described above can be carried out using a known solid-liquid separation apparatus capable of separating solid and liquid components. Examples of such solid-liquid separation apparatus include, but are not limited to, filter filtration devices using filter paper, centrifuges, screw presses, and the like.

[0053] The drying described above can be carried out using a known dryer used for drying sludge, food residues, etc. Examples of such dryers include, but are not limited to, conduction heat dryers, conduction heat vacuum dryers, hot air dryers, and combined conduction heat dryers and hot air dryers.

[0054] The aforementioned pulverization of the dried material can be carried out using a known pulverizer that physically pulverizes the dried material. While it is possible to obtain powder in a single pulverization step, it is preferable to coarsely crush the dried material first, and then further finely pulverize the resulting coarsely crushed material, as this efficiently yields a powder with smaller particle sizes. For example, the dried material can be coarsely crushed using a cutter mill, hammer mill, roll mill, etc., to a powder size that can pass through a filter with a mesh opening of 1000 μm. The resulting coarsely crushed material can then be pulverized using a roll mill, ball mill, pin mill, jet mill, etc., to obtain a powder with even smaller particle sizes. In the pulverization step, a sieving device may be used in combination to improve pulverization efficiency.

[0055] In the manufacturing method of this embodiment, undecomposed biomass is selectively removed by filtering the saccharification and fermentation residue of the raw materials through a filter with a predetermined mesh size before drying. Because the content of undecomposed biomass, which is difficult to pulverize physically, is low, it is easy to prepare a powder with a small particle size during the pulverization process.

[0056] The size of the lignin-containing powder obtained by the manufacturing method of this embodiment is not particularly limited. The lignin-containing powder obtained by the manufacturing method of this embodiment may be D 90 Preferably, the powder is 212.0 μm or less, D 90 It is more preferable that the powder is 183.0 μm or smaller, D 90 It is even more preferable that the powder is 111.0 μm or smaller, D90 It is more preferable that the powder is 107.8 μm or less, and D 90 It is particularly preferable that the powder is 88.2 μm or less. The D of the lignin-containing powder 90 The lower limit value is not particularly limited, but preferably 26.0 μm or more, and more preferably 30.0 μm or more.

[0057] The particle size of the lignin-containing powder can be measured by a particle size distribution measuring device using the laser diffraction / scattering method, and D 90 is determined from the cumulative distribution obtained by particle size measurement.

[0058] By the production method of the present embodiment, lignin powder can efficiently produce a lignin-containing powder having a high lignin content and a small particle size. Therefore, the lignin powder obtained by the production method of the present embodiment is useful as a chemical raw material, and in particular, can be utilized as an additive to resins and the like. [Examples]

[0059] The present embodiment will be described in detail below with reference to examples and the like, but the present embodiment is not limited thereto. The measurement methods of each physical property and the evaluation method of tablets in the examples and the like are as follows.

[0060] [Example 1] The raw material residue containing lignin was filtered through a mesh filter to prepare a lignin-containing powder.

[0061] As the raw material residue, we used the residue obtained after separating ethanol by distillation from the fermentation liquid obtained from ethanol fermentation in the biomass ethanol production process using sugarcane bagasse as the raw material. For the sugarcane bagasse, we used the pulverized residue left after pressing sugarcane in a roll mill to obtain sugar solution. The sugarcane bagasse was pretreated by dilute sulfuric acid pulverization at an intensity of CSI 2.108, and the resulting treated material was saccharified at 50°C for 96 hours, then inoculated with microorganisms and fermented at 32°C for 72 hours. The resulting fermented material was sterilized at 80°C for 24 hours and then cooled to around 20°C. The cooled fermented material was used as the raw material residue containing lignin.

[0062] The following eight types of mesh filters (all made of polypropylene) were used. A: Mesh Net Co., Ltd., #5-5000, mesh opening 5000μm B: Mesh Net Co., Ltd., #10-2145, Mesh opening 2145μm C: Manufactured by Tanaka Sanjiro Shoten, #12-1680, Mesh opening 1680μm D: Manufactured by Tanaka Sanjiro Shoten, #18-1000, mesh opening 1000μm E: Manufactured by Tanaka Sanjiro Shoten, #35-500, mesh opening 500μm F: Manufactured by Tanaka Sanjiro Shoten, #60-250, Mesh opening 250μm G: Manufactured by Tanaka Sanjiro Shoten, #80-177, mesh opening 177μm H: Mesh Net Co., Ltd., #121-105, Mesh opening 105μm

[0063] (1) Membrane static separation performance evaluation test After thoroughly stirring 200 mL of the raw material residue, it was poured into a small vacuum filter (228 mmHg, 0.3 atm) equipped with various mesh filters, and the time taken for complete separation was measured.

[0064] Furthermore, the concentration of suspended solids (SS) in the obtained filtrate was measured by the following method. First, the dry weight A (g) of the SS measurement filter (filter paper) ("Whatman® GF / F Glass Microfiber Filters", filter outer diameter: 47 mm, particle retention capacity: 0.7 μm, thickness: 0.42 mm) was measured. Next, 3 g of the well-mixed filtrate sample was taken and passed through a SS measurement filter by vacuum filtration to separate the solids on the filter paper. An additional 30-50 mL of pure water was poured over the filter paper, and it was vacuum filtered to wash away the water-soluble components. Then, the filter paper and the solids on it were dried together at 105°C for 24 hours, and the weight B (g) of the dried material was measured. Finally, the concentration of suspended solids (ss) was measured using the following formula.

[0065] [ss concentration (weight%)]=([B(g)]-[A(g)]) / 3(g)×100

[0066] The measurement results are shown in Table 1. In the table, in the "Result" column, "Complete Permeation" means that almost the entire amount of raw material residue was filtered out, "Gradual Blocking" means that the filter became blocked some time after the start of filtration, and "Immediate Blocking" means that the filter became blocked very quickly after the start of filtration.

[0067] [Table 1]

[0068] In test sections 1-1 and 1-2, almost the entire amount of raw material residue was filtered, and although the surface of the mesh filter was partially clogged after filtration, no deposits were observed on the back surface. Furthermore, the amount of suspended solids in the filtrate was D 90 It was larger than the raw material residue. In contrast, in test sections 1-3 to 1-8, the smaller the mesh opening of the mesh filter used, the longer the time required for filtration, and the less suspended solids there were in the filtrate. 90 A tendency for the size to decrease was observed. After filtration was completed in test sections 1-3 to 1-8, the mesh filters were completely covered with deposits on both the front and back surfaces.

[0069] (2) Evaluation test for fluid membrane separation properties After thoroughly stirring approximately 20 liters of raw material residue, the mixture was poured into an open container (a 25-liter bucket with an opening diameter of approximately 335 mm and a depth of approximately 335 mm) equipped with a mesh filter. Filter filtration was then performed, with the surface of the mesh filter being intermittently scraped with a spatula to remove any adhering residue (filter paper residue). The concentration of suspended solids (ss) in the obtained filtrate was measured using the same method as in (1) above (n=3). The average values ​​of the suspended solids (ss) concentration for each filtrate are shown in Table 2.

[0070] [Table 2]

[0071] As shown in Table 2, in test sections 2-4 to 2-8, a tendency was observed where the smaller the mesh opening of the mesh filter used, the lower the concentration of suspended solids (ss) in the filtrate and the less suspended solids there were in the filtrate. On the other hand, in test sections 2-1 to 2-3, where the mesh opening of the mesh filter was greater than 1000 μm, the concentration of suspended solids (ss) in the filtrate was almost the same as in test section 2-0, which did not use a filter, and no effect of filter filtration was observed.

[0072] Next, after filtering the entire amount of raw material residue, the residue on the mesh filter (mesh residue) was collected and a portion of it was used for compositional analysis. In addition, a portion of the filtrate was taken and the concentration of suspended solids (SS) was measured. The measurement results are shown in Table 3.

[0073] [Table 3]

[0074] Next, the remaining filtrate is filtered through a vacuum filter (Nissen MF-02-NJL, filtration area 545mm²) equipped with qualitative filter paper. 2Batch solid-liquid separation was performed using a suction pressure of -0.07 MPa. The solid component (residue on the filter paper) was collected in its entirety, dried, and subjected to compositional analysis. The concentration of suspended solids (SS) in the liquid component (filtrate) was measured. The measurement results are shown in Table 4.

[0075] [Table 4]

[0076] As shown in Table 3, in test sections 3-1 to 3-8, where the filter surface was scraped during filtration, almost the entire amount was filtered without clogging. In test sections 3-1 to 3-3, where the mesh opening of the filter used was 1680 μm or larger, the ss concentration of the filtrate after mesh filtration was approximately the same as that of the raw material residue. However, in test sections 3-4 to 3-8, where the mesh opening was 1000 μm or smaller, the smaller the mesh opening, the lower the suspended solids concentration in the filtrate. 90 A tendency towards smaller sizes was also observed.

[0077] Furthermore, as shown in Table 4, in test sections 3-1 to 3-8, where mesh filter filtration was performed, a tendency was observed for the content of cellulose and hemicellulose to decrease and the content of lignin to increase in the filter paper residue compared to the raw material residue. In particular, in test sections 3-4 to 3-8, where the mesh opening of the filter used was 1000 μm or less, the decrease in the content of cellulose and hemicellulose was large, and the increase in the content of lignin was also large.

[0078] (3) Evaluation of the pulverizability of filter paper residue After drying the filter paper residue obtained in (2) above, each dried material was coarsely crushed in a cutter mill to a mesh size that could pass through a 1 mm mesh opening. Next, 300 g of the cutter milled material was taken and ground in a ball mill for 12 hours to obtain a pulverized material (lignin-containing powder). 20 g of the pulverized material was taken at 0.5, 1.0, 2.0, 3.0, 4.5, 6.0, 9.0 and 12.0 hours from the start of grinding. The ball milled material was subjected to particle size distribution measurement with n=3, and its D 10 ~D 90The pulverizability was evaluated based on the average particle size. The measurement results of the particle size distribution for each sample are shown in Tables 5 to 13.

[0079] [Table 5]

[0080] [Table 6]

[0081] [Table 7]

[0082] [Table 8]

[0083] [Table 9]

[0084] [Table 10]

[0085] [Table 11]

[0086] [Table 12]

[0087] [Table 13]

[0088] For comparison, sugarcane bagasse itself was coarsely crushed in a cutter mill to a mesh size that could pass through a 1 mm mesh opening. 300 g of the resulting cutter mill pulverized material was then taken and ground in a ball mill for 12 hours to obtain a pulverized material. The particle size distribution of the ball mill pulverized sugarcane bagasse after 12 hours of grinding was measured in the same manner. As a result, the D of the ball mill pulverized sugarcane bagasse was 90 The particle size was 951.8 μm, which was nearly 10 times larger than the pulverized material (Table 13) of lignin-containing powder after 12 hours of pulverization without mesh filter filtration. This result indicates that lignin-containing powder with small particle sizes can be produced by using saccharification and fermentation residue that has not been dried, rather than sugarcane bagasse itself. Sugarcane bagasse is difficult to pulverize because it is a large-particle, long, undecomposed biomass with remaining plant cell walls, whereas saccharification and fermentation residue is easy to pulverize because it contains a large amount of lignin with loosened fibers.

[0089] As shown in Tables 5-13, lignin-containing powders prepared using mesh filters (D-H) with mesh openings of 105 μm to 1000 μm showed that the smaller the mesh opening, the lower the D. 90 A tendency for the value to decrease was observed. In particular, lignin-containing powder prepared using mesh filters (E to H) with mesh openings of 105 μm to 500 μm showed a lower D value than lignin-containing powder prepared without mesh filter filtration, regardless of grinding time. 90 The amount was small. Based on these results, by filtering the saccharification and fermentation residue in a wet state using a mesh filter with a mesh opening of 105 μm to 1000 μm to reduce the content of undecomposed biomass, D can be produced at a low energy cost. 90 It was revealed that it is possible to prepare lignin-containing powders with small particle sizes.

[0090] [Example 2] The lignin-containing raw material residue used in Example 1 was filtered using three mesh filters with mesh openings of 1000 μm, 512 μm, and 276 μm while intermittently stirring. The 1000 μm sieve-down and 512 μm sieve-up portion (the sediment that passed through the 1000 μm mesh filter and was collected on the 512 μm mesh filter) and the 276 μm sieve-down portion (the solids that passed through the 276 μm mesh filter) were recovered.

[0091] The shape and size of the particles in each category were investigated using particle shape imaging. While particle size distribution is investigated using infrared spectroscopy, particle shape imaging involves collecting approximately 10,000 photographs of individual particles flowing through a flow cell. By analyzing these photographs, particle size, circularity, etc., can be derived, making it possible to measure not only particle diameter but also characteristic quantities focusing on the particle's shape. Specifically, a particle shape imaging analyzer (PITA-04, manufactured by Seishin Co., Ltd.) was used to photograph the particles in each category in a wet dispersion, and the shape and size of individual particles were analyzed through image analysis.

[0092] The equivalent circle diameter and circularity were examined and compared for particles in the 512 μm sieve portion below the 1000 μm sieve portion (hereinafter sometimes referred to as the "512 μm sieve portion") and particles in the 276 μm sieve portion. Here, the equivalent circle diameter (μm) corresponds to the diameter of a true circle corresponding to the area of ​​the shadow (projected area: S) of the photograph. The circularity is a value that is the square of the value obtained by dividing the circumference of the true circle made up by the perimeter of the shadow (projected perimeter: P) of the photograph, with a true circle having a value of 1.0.

[0093]

number

[0094] Figure 1 shows a two-dimensional plot of circularity and equivalent diameter for particles in the 512 μm sieve-up section and the 276 μm sub-sieve section. As shown in Figure 1(A), the particles in the 512 μm sieve-up section had a large equivalent diameter and were distributed across a wide range of circularities. Furthermore, a tendency was observed for circularity to decrease as the equivalent diameter increased. This was presumed to be due to the presence of large particles, such as fibrous undegraded biomass. In contrast, as shown in Figure 1(B), the particles in the 276 μm sub-sieve section were mostly composed of particles with an equivalent diameter of less than 10 μm, and a tendency for high circularity was observed. This was presumed to be because most of the small-particle lignin was in the form of aggregates, resulting in a high distribution of circularity.

[0095] Figure 2 shows photographs of representative examples of particles in the 512 μm sieve-up section and the 276 μm sieve-down section. In the figure, X represents the equivalent diameter of a circle (μm), and Y represents the degree of circularity. As shown in Figure 2(A), many rectangular fibers and steel wool-like structures were observed in the 512 μm sieve-up section. In contrast, as shown in Figure 2(B), the particles in the 276 μm sieve-down section showed aggregated particles in a nearly circular shape, with the fibrous structure decomposed and only lignin remaining. These results confirm that when filtering saccharification and fermentation residue in a wet state, using a mesh filter with an opening of 500 μm or less allows for the selective removal and separation of large-particle fibers like those seen in Figure 2(A), while selectively retaining small-particle substances without fibrous structures like those seen in Figure 2(B). [Industrial applicability]

[0096] The method for producing lignin-containing powder according to this embodiment allows for the preparation of lignin-containing powder with a high lignin content and smaller particle size, which is useful as a chemical raw material, from the lignin-containing residue generated during the saccharification or fermentation of lignocellulosic biomass. Therefore, this production method and lignin-containing powder are extremely useful for the effective utilization of lignocellulosic biomass, which is industrial waste such as that used in biomass ethanol production.

Claims

1. The residue or solution containing lignin, generated during the saccharification or fermentation of lignocellulosic biomass, is filtered in a wet state by filter filtration. The resulting filtrate is subjected to solid-liquid separation, the resulting solid residue is dried, and the resulting dried material is pulverized to produce a lignin-containing powder. A method for producing lignin-containing powder, wherein the filtration is performed using a filter with a mesh opening of 105 μm to 1000 μm.

2. The method for producing lignin-containing powder according to claim 1, wherein the mesh opening of the filter is 170 μm to 500 μm.

3. The method for producing a lignin-containing powder according to claim 1, wherein in the filtration, at least a portion of the deposits on the surface of the filter is removed once or more times.

4. The filtration is performed using a filter filtration device equipped with a mechanism to prevent clogging of the filter. The method for producing lignin-containing powder according to claim 1, wherein the clogging suppression mechanism is a scraping mechanism configured to continuously or intermittently scrape off deposits on the surface of the filter, or a vibration mechanism configured to continuously or intermittently vibrate the filter.

5. The method for producing lignin-containing powder according to claim 1, wherein the residue or solution is a saccharified liquid, fermented liquid, distillation wastewater, or residue obtained by solid-liquid separation therefrom, generated in the process of saccharifying or fermenting lignocellulosic biomass.

6. The method for producing a lignin-containing powder according to claim 1, wherein the pulverization is carried out by coarsely crushing the dried material and then further finely crushing the resulting coarsely crushed material.

7. The powder D ９０ The method for producing a lignin-containing powder according to claim 1, wherein the particle size is 212.0 μm or less.

8. The powder D ９０ The method for producing a lignin-containing powder according to claim 1, wherein the particle size is 107.8 μm or less.

9. The powder D ９０ The method for producing lignin-containing powder according to claim 1, wherein the particle size is 88.2 μm or less.

10. Using lignin-containing residue or solution produced during the saccharification or fermentation process of lignocellulosic biomass as a raw material, D ９０ A lignin-containing powder with a particle size of 88.2 μm or less.

Images