Method for producing lignin-containing powder

Abstract

Provided is a method for producing a powder having a high lignin content and a smaller particle size from saccharification / fermentation residues of lignocellulosic biomass. 【Solution means】A residue or solution containing lignin generated during the process of saccharifying or fermenting lignocellulosic biomass 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 product is pulverized to produce a powder containing lignin. The filtration is performed using a filter with a mesh opening of 105 μm to 1000 μm. A method for producing a lignin-containing powder.

Description

Technical Field

[0001] The present invention relates to a method for producing a powder containing lignin from saccharified and fermented residues of lignocellulosic biomass.

Background Art

[0002] As one of the efforts towards realizing a post-fossil resource-based society in recent years, the development of biomass utilization technologies has been promoted. While the production of bioethanol using sugarcane, corn, etc. as raw materials is expanding, the development of non-edible biomass utilization technologies aimed at avoiding competition with food production and effectively utilizing limited resources has been advanced. Non-edible biomass mainly includes plant biomass (lignocellulosic biomass) composed of three components: cellulose, hemicellulose, and lignin. These three components are twisted and solidified in a fibrous form at the molecular level, and a strong plant cell wall is formed so that they are laminated, constituting the stems and leaves of the plant itself.

[0003] The production of ethanol using lignocellulosic biomass as a raw material consists of a pretreatment step of thermochemically pretreating the biomass raw material, a saccharification step of enzymatically treating the biomass after the pretreatment step to produce a saccharified solution, a fermentation step of adding a microbial culture solution to the saccharified solution obtained in the saccharification step to perform ethanol fermentation, and a purification step of separating ethanol from the fermentation broth 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 a high yield, high-yield and economical ethanol production becomes possible.

[0004] In the production of ethanol, there is a problem that a large amount of fermentation residue is generated because lignin in the biomass raw material remains as a solid. On the other hand, when lignin is decomposed, phenol derivatives and the like can be obtained, so it can be used as a raw material for chemical industrial products such as resin raw materials, composite materials, and surfactants. Therefore, the development of technologies for utilizing the saccharification and fermentation residues discharged from the cellulose ethanol production process and the like as chemical raw materials is underway, and related patents can also be found. The saccharification and fermentation residues discharged from the cellulose ethanol production process and the like are likely to have high-purity lignin, lignin with a low degree of modification can be obtained through a mild biomass decomposition process, and it can be supplied inexpensively and stably as an industrial residue such as ethanol production residue. Therefore, it is expected to be a candidate for raw material resources for chemical production processes mainly using a large amount of lignin.

[0005] Cellulose, hemicellulose, and lignin all have different chemical structures and properties. Therefore, when these are treated as substitutes for chemical product raw materials, it is required to recover the target component with high purity and high yield. For example, in the above-mentioned method of utilizing any one or two of the three components, the remaining components cannot be effectively utilized, so the yield per unit biomass is low as it is, and the cost is likely to increase. In order to construct a highly economically rational process for effectively utilizing lignocellulosic biomass, the development of technologies for effectively utilizing its by-product residue components also becomes an issue.

[0006] For example, Patent Document 1 discloses an invention related to a system for recovering organically solvent-soluble lignin from residues generated in the process of producing bioethanol from cellulose and hemicellulose in lignocellulosic biomass. Further, Patent Document 2 discloses an invention related to a rubber composition for studless tires with improved ice performance by blending water-insoluble lignin extracted from fermentation residues. Furthermore, it is possible to selectively liquefy and extract lignin by selectively chemically modifying lignin with sulfonic acid groups, phenol groups, PEG groups, etc. to change its solubility. Patent Document 3 discloses an invention related to a method for separating lignin in high yield as modified lignin by allowing a phenol compound to act on fermentation residues in ethanol production.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] When using saccharification / fermentation residues as raw materials for chemical products, it is preferable that their quality is stable. However, lignocellulosic biomass is a natural product, and in addition to the raw material composition varying depending on the plant species and parts, it is also affected by factors such as spoilage and poor growth, and its composition is not necessarily stable. These effects also affect the saccharification / fermentation performance, and even for saccharification / fermentation residues by-produced under the same process / production conditions, their composition cannot be uniform. In addition to the uncertainty of these biomass compositions themselves, due to the characteristics of the manufacturing process, it is difficult to achieve a process of completely decomposing and saccharifying cellulose and hemicellulose by 100%, and impurities other than lignin such as cellulose and hemicellulose are inevitably mixed in the saccharification / fermentation residues.

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

Means for Solving the Problems

[0010] That is, the present invention includes the following aspects. (1) A residue containing lignin or a solution containing the same generated in the process of saccharifying or fermenting lignocellulosic biomass 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 product is pulverized to produce a powder containing lignin. The method for producing a lignin-containing powder, wherein the filtration is performed using a filter having a mesh opening of 105 μm to 1000 μm. (2) The method for producing a lignin-containing powder according to (1) above, wherein the mesh opening of the filter is 170 μm to 500 μm. (3) The method for producing a lignin-containing powder according to (1) or (2) above, wherein in the filtration, at least a part of the deposits on the surface of the filter is peeled off one or more times. (4) The filtration is performed using a filter filtration device equipped with a clogging prevention mechanism for the filter. The clogging suppression mechanism is a scraping mechanism configured to scrape deposits on the surface of the filter continuously or intermittently, or a vibration mechanism configured to vibrate the filter continuously or intermittently. The method for producing lignin-containing powder according to any one of (1) to (3) above. (5) The method for producing 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 drainage liquid 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 lignin-containing powder according to any one of (1) to (5) above, wherein the pulverization is performed by 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 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 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 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, D 90 The lignin-containing powder, which is 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

Figure 2

Mode for Carrying Out the Invention

[0013] Hereinafter, a mode 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, shii, 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, miscanthus, napier grass, etc.; jatropha, cashew, etc.

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

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

[0017] "Lignin" has a basic skeleton composed of aromatic nuclei (benzene nuclei), and based on its structure, it is classified into G nuclei, S nuclei, and H nuclei. A G nucleus has one methoxy group (-OCH3) at the ortho position of the phenolic skeleton part, an S nucleus has two methoxy groups at the ortho position, and an H nucleus has no methoxy group at the ortho position. Also, lignin in herbaceous biomass such as bagasse contains all of H nuclei, G nuclei, and S nuclei as its basic skeleton. Among lignins derived from woody biomass, lignin derived from conifers has a G nucleus as its basic skeleton, and lignin derived from broad-leaved trees has G nuclei and S nuclei as its basic skeleton.

[0018] "Cellulose" contains hexoses with six carbons as its constituent units. Therefore, when cellulose undergoes hydrolysis, it produces monosaccharides (such as glucose) of hexoses consisting of six carbons or oligosaccharides (such as cellobiose) of hexoses in which multiple of these monosaccharides are linked.

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

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

[0021] The residue used as a raw material in the production method of the present embodiment is a residue containing lignin generated in the process of saccharifying or fermenting lignocellulosic biomass (hereinafter, may be referred to as "saccharification-fermentation residue of lignocellulosic biomass" or simply abbreviated as "saccharification-fermentation residue"). By saccharification or fermentation, cellulose and hemicellulose in lignocellulosic biomass are consumed. That is, the saccharification-fermentation residue of lignocellulosic biomass is a residue in which at least a part of cellulose and hemicellulose is decomposed and consumed.

[0022] A large amount of energy is required to directly micronize herbaceous biomass or woody biomass. In the production method of the present embodiment, by using the saccharification-fermentation residue as a raw material, a powder containing lignin suitable as a chemical product raw material can be efficiently produced with less energy.

[0023] The saccharification-fermentation residue necessarily contains undecomposed biomass in addition to the biomass decomposed by saccharification-fermentation. The saccharification-fermentation residue mixed with this undecomposed biomass has poor micronization efficiency, a long required time for micronization, and a large crushing power. In the production method of the present embodiment, the undecomposed biomass is efficiently removed by filtering the saccharification-fermentation residue of the raw material in a wet state using a filter with a specific mesh opening. Thereby, a powder containing lignin can be produced with extremely high energy efficiency.

[0024] Examples of the saccharified / fermented residue or the solution containing the same used in the production method of the present 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 the raw material in the production method of the present embodiment, a residue or a solution containing the same generated in the process of producing biochemcials using lignocellulosic biomass as the raw material can be used. Examples of the biochemicals include alcohols such as bioethanol, biobutanol, and propanediol, amino acids, organic acids such as citric acid, lactic acid, and succinic acid. As the saccharified / fermented residue or the solution containing the same used as the raw material in the production method of the present embodiment, a saccharified solution, a fermentation broth, a distillation effluent generated in the process of producing bioethanol using lignocellulosic biomass as the raw material, or a residue obtained by solid-liquid separation from these is preferable, and a saccharified residue remaining after pretreating lignocellulosic biomass by a dilute sulfuric acid hydrolysis method and further decomposing the obtained pretreated raw material by an enzymatic saccharification method is particularly preferable.

[0025] By saccharification and fermentation treatment, cellulose and hemicellulose in lignocellulosic biomass are decomposed, and its cell wall structure and fiber structure are disrupted. Therefore, the saccharification and fermentation residue of lignocellulosic biomass mainly contains cellulose and hemicellulose that could not be completely saccharified, lignin micronized by the disruption of the cell wall structure, etc., and undegraded biomass having a plant cell wall and fiber structure. In addition, in some cases, foreign substances derived from the raw lignocellulosic biomass and the manufacturing process are also included. When the saccharification and fermentation residue is directly dried and then pulverized, these components other than lignin are also incorporated into the powder, so that the lignin content ratio is suppressed to be low. In addition, the lignin in the saccharification and fermentation residue easily adheres to undegraded biomass in the form of fibrous material during drying to form aggregates with a large apparent particle size. Since undegraded biomass is difficult to crush by physical pulverization treatment, the powder obtained by pulverizing the dried saccharification and fermentation residue has a large proportion of large particles. Although the large particles in the obtained powder can be removed by a dry sieve or the like, the lignin aggregated with foreign substances and undegraded biomass is also removed together, resulting in a decrease in the recovery efficiency of lignin.

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

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

[0028] The intensity of the pretreatment, that is, the intensity of decomposing lignin, cellulose, and hemicellulose can be controlled by three parameters: temperature, time, and pH. Therefore, the treatment intensity can be evaluated by the CSI (Combined Severity Index) represented by the following formula (I) with the above three parameters as variables. Note that the larger the CSI value, the higher the decomposition intensity of the biomass tends to be, and the smaller the CSI value, the lower the decomposition intensity of the biomass tends to be. By setting the pretreatment conditions so that the CSI, which is a value calculated from formula (I), is within a predetermined range, the target decomposition intensity can be achieved.

[0029] [Number]

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

[0031] The higher the decomposition intensity of the biomass, that is, the larger the CSI value, the more likely it is to obtain a residue containing a large amount of organosolv-soluble lignin. Therefore, as the pretreatment of the saccharification and fermentation residue used in the production method of this embodiment, it is preferably carried out under the condition that the CSI is 1.0 or more and 3.0 or less, more preferably 1.2 or more and 2.8 or less, still more preferably 1.5 or more and 2.7 or less, and particularly preferably 1.5 or more and 2.5 or less. When the CSI is equal to or higher than the above lower limit value, the production amount of organosolv-soluble lignin in the pretreatment can be further improved, and the enzymatic saccharification rate of C5 and C6 sugars can be further improved. On the other hand, when the CSI is equal to or lower than the above upper limit value, the production of furfural due to over-decomposition of xylose can be more effectively suppressed, and the decrease in the enzymatic saccharification rate of C5 and C6 sugars can be more effectively suppressed.

[0032] In the pretreatment step, as specific treatment conditions within the above CSI range, the pH can be 0.8 or more and less than 1.5, can be 0.8 or more and 1.4 or less, and can be 0.8 or more and 1.2 or less.

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

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

[0035] The reaction vessel used in the dilute sulfuric acid hydrolysis method is not particularly limited as long as it is a steam supply type, but it has a heating and pressure device such as an acid-resistant autoclave or an acid-resistant heating and pressure vessel, and further, a form in which it is placed in a device such as a device integrated with a screw feeder and capable of continuously performing treatment is conceivable.

[0036] In the pretreatment step, the biomass may be pulverized using a mill or the like before and after the treatment by the dilute sulfuric acid hydrolysis method.

[0037] The saccharification treatment after the pretreatment is carried out using an enzyme with the cellulose and hemicellulose contained in the lignocellulosic biomass after the pretreatment as substrates. The enzyme mentioned here is mainly a saccharifying enzyme. Examples of the saccharifying enzyme include cellulase that decomposes cellulose, hemicellulase that decomposes hemicellulose, and amylase that decomposes starch.

[0038] The cellulase may be any that decomposes cellulose into monosaccharides or oligosaccharides such as glucose. For example, those having at least one activity among the activities of endoglucanase (EG), cellobiohydrolase (CBH), and β-glucosidase (BGL) are mentioned, and it is preferable from the viewpoint of enzyme activity that it is an enzyme mixture having these respective activities.

[0039] The hemicellulase may be any enzyme that decomposes hemicellulose into monosaccharides or oligosaccharides such as xylose. For example, those having at least one activity among the activities of xylanase, xylosidase, mannanase, galactosidase, glucuronidase, and arabinofuranosidase can be mentioned. From the viewpoint of enzyme activity, it is preferable that these are enzyme mixtures having each activity.

[0040] The origin of these saccharifying enzymes such as cellulase and hemicellulase is not limited. For example, cellulase and hemicellulase and other saccharifying enzymes derived from microorganisms such as the genus Trichoderma, the genus Acremonium, the genus Aspergillus, the genus Bacillus, the genus Pseudomonas, the genus Penicillium, the genus Aeromonus, the genus Irpex, the genus Sporotrichum, and the genus Humicola can be used.

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

[0042] There are no particular limitations on the saccharification process, and it can be carried out using a known saccharification apparatus. Specifically, saccharification apparatuses such as a stirring type, an aeration stirring type, a bubble column type, a fluidized bed type, and a packed bed type can be mentioned. Further, the saccharification apparatus may be provided with a temperature control device such as a hot water circulation type jacket outside the apparatus in order to keep the temperature inside the apparatus constant.

[0043] The fermentation treatment is carried out while adding the saccharified liquid obtained by the saccharification treatment, the saccharification residue adsorbed with the saccharifying enzyme, and microorganisms, and stirring. The saccharification residue contains polysaccharides such as non-saccharified cellulose and hemicellulose, and the saccharifying enzyme adsorbed to the saccharification residue. Therefore, in the fermentation treatment, by using both the saccharified liquid and the saccharification residue obtained in the saccharification treatment, the saccharification reaction can be simultaneously carried out during the fermentation reaction to generate monosaccharides and oligosaccharides that serve as substrates in the fermentation by microorganisms.

[0044] The fermentation conditions may be appropriately carried out based on the prior art. For example, the fermentation temperature is preferably 25°C or higher and 50°C or lower, more preferably 28°C or higher and 35°C or lower, and particularly preferably 32°C. Also, the fermentation time is preferably 24 hours or longer and 120 hours or shorter, more preferably 24 hours or longer and 96 hours or shorter, and even more preferably 24 hours or longer and 72 hours or shorter.

[0045] There is no particular limitation on the microorganisms to be used as long as they can produce the target lignocellulosic biomass-derived compounds. Specifically, examples include yeasts and bacteria, and genetically modified microorganisms are also preferably used.

[0046] In the production method of the present embodiment, the saccharification / fermentation residue is filtered by a filter filtration method while in a wet state. If the saccharification / fermentation residue is dried, lignin will aggregate with each other during drying, resulting in a particle size larger than that of the undigested biomass. Even if the dried product after such large-particle-size materials are formed is pulverized and sieved, the micronized lignin will be entangled with the large-particle-size materials due to electrostatic aggregation or the like, and the yield of the micronized lignin by filter filtration will be significantly reduced. In the production method of the present embodiment, by filtering the residue obtained in the saccharification / fermentation process directly without drying, foreign substances and undigested biomass can be removed without significantly reducing the recovery rate of lignin. In particular, undigested biomass often takes a fibrous high aspect ratio-like form, and the major axis ranges widely from about several millimeters to about several hundred micrometers. Therefore, undigested biomass with a long major axis can be efficiently removed by a filter having a mesh structure. In the production method of the present embodiment, in particular, by using a filter with a mesh opening of 105 μm to 1000 μm, undigested biomass can be selectively removed while recovering the micronized lignin.

[0047] In the production method of the present embodiment, the saccharification / fermentation residue to be 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 effluent after ethanol distillation separation obtained in the cellulose ethanol production process as the saccharification / fermentation residue of the raw material, the saccharification / fermentation residue recovered by subjecting the distillation effluent to decanter centrifugation can be used as the raw material for filter filtration, but it is preferable to directly use the distillation effluent as the raw material for filter filtration.

[0048] By making the mesh opening of the filter used for filtration small enough, foreign substances and undigested biomass can be removed by filtration more efficiently. On the other hand, since the saccharification / fermentation residue contains a large amount of various solids, it is likely to be clogged when the mesh opening is small. In the production method of the present embodiment, the mesh opening of the filter used for filter filtration is not particularly limited as long as it is in the range of 105 μm to 1000 μm. However, from the viewpoint of being excellent in both the separation performance between other components including undigested biomass and lignin and the separation and recovery efficiency (difficulty of clogging) of filter filtration, it is preferably in the range of 105 μm to 500 μm, more preferably in the range of 170 μm to 500 μm, and even more preferably in the range of 177 μm to 500 μm. By setting the mesh opening of the filter used for filter filtration to 500 μm or less, it is possible to produce a powder suitable as a chemical product raw material, in which the proportion of particles with high roundness, small aspect ratio, and small particle size is large.

[0049] Since the saccharification / fermentation residue of lignocellulosic biomass contains a large amount of fibrous substances including undigested biomass, finer fibers are trapped around the long fibrous undigested biomass and the like recovered on the filter surface, and finally a muddy self-film is formed on the filter surface. Due to the clogging caused by this self-film formation, even fine particle lignin is recovered on the filter surface, and the recovery rate of lignin is significantly reduced. Therefore, in the production method of the present embodiment, in the above filter filtration, it is preferable to perform a treatment of peeling off at least a part of the deposits on the filter surface one or more times. By peeling off the deposits on the filter surface, the clogging of the filter can be eliminated. The method of peeling off the deposits is not particularly limited, and it may be performed manually or a filter filtration apparatus equipped with a filter clogging suppression mechanism may be used.

[0050] Examples of clogging prevention mechanisms for filters include scraping mechanisms configured to continuously or intermittently scrape deposits on the filter surface, and vibration mechanisms configured to continuously or intermittently vibrate the filter. As a filter filtration device equipped with a clogging prevention mechanism used in the manufacturing method of this embodiment, it 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. As the scraping mechanism, any structure that can scrape off deposits on the surface by rubbing on the filter surface may be used, for example, a scraper. The scraper may be blade-shaped (also referred to as knife-shaped or blade-shaped), or spatula-shaped. As the vibration mechanism, a mechanism that vibrates the entire filter may be used, or a linear structure that constitutes the mesh of the filter may be vibrated respectively. Specifically, examples of the vibration mechanism include a continuous belt filter, a vibrating screen, an ultrasonic vibrating screen, etc. In addition, a continuous moving filter mechanism can also be used. This mechanism continuously or intermittently replaces the filter, so that the filter itself is continuously refreshed, the filter itself transports the cake (saccharified and fermented residue used for filter filtration), and the cake does not continue to accumulate on the filter. For example, in a belt conveyor shape, the filtered part (active) and the unfiltered part (non-active) continuously alternate, and a mechanism that scrapes off the cake when not filtering.

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

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

[0053] The drying 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, combined types of conduction heat dryers and hot air dryers, etc.

[0054] The pulverization of the dried product can be carried out using a known pulverizer that physically pulverizes the dried product. Also, it may be pulverized into powder in one step, but from the point of efficiently obtaining powder with a smaller particle size, it is preferable to roughly pulverize the dried product and then further finely pulverize the obtained roughly pulverized product. For example, the dried product is roughly pulverized into powder of a size that can pass through a filter with a mesh opening of 1000 μm using a cutter mill, hammer mill, roll mill, etc., and then the obtained roughly pulverized product is finely pulverized using a roll mill, ball mill, pin mill, jet mill, etc. to obtain powder with a smaller particle size. In the fine pulverization process, it may be combined with a screening device to improve the pulverization efficiency.

[0055] In the production method of this embodiment, by filtering with a filter having a predetermined mesh opening before drying the saccharification and fermentation residue of the raw material, undegraded biomass is selectively removed. Since the content of undegraded biomass that is difficult to physically pulverize is small, it is easy to prepare powder with a small particle size in the pulverization process.

[0056] The size of the lignin-containing powder obtained by the production method of this embodiment is not particularly limited. As the lignin-containing powder obtained by the production method of this embodiment, it is preferably a powder with D 90 of 212.0 μm or less, more preferably a powder with D 90 of 183.0 μm or less, and even more preferably a powder with D 90 of 111.0 μm or less, and D90 It is more preferably a powder with a particle size of 107.8 μm or less, and D 90 Particularly preferably, it is a powder with a particle size of 88.2 μm or less. The D of the lignin-containing powder 90 The lower limit value is not particularly limited, but is 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 used as an additive to resins and the like.

Examples

[0059] Examples and the like will be given below to explain the present embodiment in detail, but the present embodiment is not limited thereto. The measurement methods of each physical property and the evaluation method of tablets in 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, the residue after separating ethanol by distillation from the fermentation broth obtained by ethanol fermentation in the production process of biomass ethanol using sugarcane bagasse as the raw material was used. As the sugarcane bagasse, the pulverized material of the squeezed residue after obtaining a sugar solution by squeezing sugarcane with a roll mill was used. The sugarcane bagasse was pretreated at a strength of CSI = 2.108 by the dilute sulfuric acid steaming method, and the obtained treated material was saccharified at 50 °C for 96 hours, then inoculated with microorganisms and fermented at 32 °C for 72 hours. The obtained fermented product was sterilized under the conditions of 80 °C for 24 hours, and then cooled to around 20 °C. The fermented product after cooling was used as the raw material residue containing lignin.

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

[0063] (1) Membrane static separation property 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 each mesh filter, and the time taken until complete separation was measured.

[0064] Furthermore, the concentration of suspended substances (ss) in the obtained filtrate was measured by the following method. First, the dry weight A (g) of the filter paper for SS measurement (Whatman (registered trademark) 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-stirred filtrate sample was collected, and the solid content on the filter paper was separated through the filter paper for SS measurement by vacuum filtration. An additional 30 - 50 mL of pure water was poured over the filter paper and vacuum-filtered to wash away the water-soluble components. Then, the filter paper and the solid matter on it were treated at 105°C for 24 hours while still in one piece to dry them, and the dry matter weight B (g) was measured. Finally, the suspended solid (ss) concentration was measured using the following formula.

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

[0066] The measurement results are shown in Table 1. In the table, in the "Result" column, "Complete Transparency" means that almost all of the raw material residue was filtered, "Gradual Blockage" means that the filter became blocked some time after the start of filtration, and "Immediate Blockage" means that the filter became blocked promptly after the start of filtration.

[0067]

Table 1

[0068] In Test Sections 1-1 and 1-2, almost all of the raw material residue was filtered. Although the surface of the mesh filter after filtration was partially clogged, no deposits were observed on the back surface. Also, the suspended solids D in the filtrate 90 were larger than those of the raw material residue. In contrast, in Test Sections 1-3 to 1-8, as the mesh opening of the used mesh filter became smaller, the filtration time became longer, the amount of suspended solids in the filtrate decreased, and a tendency for D 90 to decrease was observed. After filtration in Test Sections 1-3 to 1-8, both the front and back surfaces of the mesh filter were completely covered with deposits.

[0069] (2) Flow membrane separation property evaluation test After thoroughly stirring about 20 L of raw material residue, it was poured into an open container (a 25 L bucket with an opening diameter of about 335 mm and a depth of about 335 mm) equipped with each mesh filter, and while intermittently scraping the surface of the mesh filter with a spatula to remove the adhering residue (filter paper residue), filter filtration was performed. The suspended solid (ss) concentration of the obtained filtrate was measured in the same manner as in (1) above (n = 3). The results of the suspended solid (ss) concentration (average value) of each filtrate are shown in Table 2.

[0070]

Table 2

[0071] As shown in Table 2, in Test Sections 2-4 to 2-8, the smaller the mesh opening of the used mesh filter, the smaller the suspended solid (ss) concentration of the filtrate and the smaller the amount of suspended solids in the filtrate tended to be observed. On the other hand, the suspended solid (ss) concentration of the filtrate in Test Sections 2-1 to 2-3 where the mesh opening of the mesh filter was more than 1000 μm was almost the same as that of Test Section 2-0 without a filter, and the effect of filter filtration was not observed.

[0072] Next, after filtering the entire amount of the raw material residue, the residue (mesh residue) on the mesh filter was recovered, and a composition analysis was performed using a part of it. Also, a part of the filtrate was separated, and the suspended solid (ss) concentration was measured. The measurement results are shown in Table 3.

[0073]

Table 3

[0074] Next, the entire remaining amount of the filtrate was filtered using a vacuum filter (manufactured by Nissen, MF-02-NJL, filtration area 545 mm 2Batch solid-liquid separation was carried out at an attractive pressure of -0.07 MPa. The solid content (residue on filter paper) was recovered in its entirety, dried, and subjected to compositional analysis. For the liquid fraction (filtrate), the concentration of suspended substances (ss) 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 filtration was carried out while scraping the filter surface, almost the entire amount was filtered without clogging. In Test Sections 3-1 to 3-3 where the aperture of the filter used was 1680 μm or more, the ss concentration of the filtrate after the mesh filter was almost the same as that of the raw material residue. However, in Test Sections 3-4 to 3-8 where the aperture was 1000 μm or less, the lower the aperture, the lower the concentration of suspended substances in the filtrate, and a tendency for D 90 to also become smaller was observed.

[0077] Also, as shown in Table 4, in Test Sections 3-1 to 3-8 where mesh filter filtration was carried out, in the filter paper residue, the content ratios of cellulose and hemicellulose tended to decrease and the content ratio of lignin tended to increase compared to the raw material residue. In particular, in Test Sections 3-4 to 3-8 where the aperture of the filter used was 1000 μm or less, the decrease in the content ratios of cellulose and hemicellulose was large, and the increase ratio of the content ratio of lignin was also large.

[0078] (3) Evaluation of grindability of filter paper residue After drying the filter paper residue obtained in (2) above, each dried product was roughly crushed with a cutter mill to a mesh passing size of 1 mm aperture. Next, 300 g of the cutter mill crushed product was taken, and pulverized with a ball mill for 12 hours to obtain a pulverized product (powder containing lignin). At 0.5, 1.0, 2.0, 3.0, 4.5, 6.0, 9.0, and 12.0 hours after the start of pulverization, 20 g portions of the pulverized product were taken. The ball mill pulverized product was subjected to particle size distribution measurement with n = 3, and its D 10 ~D 90Based on the particle size (average value), the grindability was evaluated. The measurement results of the particle size distribution of 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] As a comparison target, sugarcane bagasse itself was coarsely crushed with a cutter mill to a mesh passing size of 1 mm opening, and then 300 g of the obtained cutter mill crushed product was taken and pulverized with a ball mill for 12 hours to obtain a pulverized product. For the ball mill pulverized product of sugarcane bagasse after 12 hours of pulverization, particle size distribution measurement was similarly performed. As a result, the D 90 of the ball mill pulverized product of sugarcane bagasse was 951.8 μm, which was nearly 10 times larger than that of the pulverized product after 12 hours of pulverization of the lignin-containing powder without mesh filter filtration treatment (Table 13). This result indicates that by using the saccharification and fermentation residue that has not been dried even once instead of sugarcane bagasse itself, a lignin-containing powder with a small particle size can be produced. Since sugarcane bagasse is a large-particle-size and long undegraded biomass with plant cell walls remaining, it is difficult to pulverize, while the saccharification and fermentation residue contains a large amount of lignin with loosened fibers and is thus easy to pulverize.

[0089] As shown in Tables 5 to 13, for the lignin-containing powders prepared using mesh filters (D to H) with a mesh opening of 105 μm to 1000 μm, the smaller the mesh opening, the tendency for D 90 to become smaller was observed. In particular, the lignin-containing powders prepared using mesh filters (E to H) with a mesh opening of 105 μm to 500 μm had a smaller D 90 than the lignin-containing powder prepared without mesh filter filtration regardless of the pulverization time. From these results, by filtering the saccharification and fermentation residue in a wet state through a mesh filter with a mesh opening of 105 μm to 1000 μm to reduce the content of undegraded biomass, it became clear that a lignin-containing powder with a small D 90 can be prepared with low energy costs.

[0090] [Example 2] The raw material residue containing lignin used in Example 1 was filtered while intermittently stirring using three mesh filters with mesh openings of 1000 μm, 512 μm, and 276 μm, and the fraction below 1000 μm and above 512 μm (the deposit collected on the filter of the 512 μm mesh filter after passing through the 1000 μm mesh filter) and the fraction below 276 μm (the solid content passing through the 276 μm mesh filter) were recovered.

[0091] The shape and size of the particles contained in each fraction were examined by the particle shape image measurement method. Regarding the particle size distribution using infrared spectroscopy, in the particle shape image measurement method, about 10,000 photos of each particle flowing through the flow cell are collected, and by performing image analysis of these photos to derive the particle size, roundness, etc., it is possible to measure characteristic quantities focusing not only on the particle size but also on its shape. Specifically, using a particle shape image analyzer (PITA - 04, manufactured by Seishin Co., Ltd.), the particles contained in each fraction were photographed in a wet dispersion liquid, and the shape and size of each particle were analyzed by image analysis.

[0092] For the particles in the fraction below 1000 μm and above 512 μm (hereinafter sometimes referred to as the "fraction above 512 μm") and the particles in the fraction below 276 μm, the equivalent circular diameter and roundness were examined and compared. Here, the equivalent circular diameter (μm) is obtained by integrating the area of the shadow in the photo (projection area: S) and corresponds to the diameter of a perfect circle equivalent to that area. The roundness is a numerical value equivalent to the square of the value obtained by dividing the circumference of the perfect circle formed by the equivalent circular diameter by the perimeter of the shadow in the photo (projection perimeter: P), and a perfect circle has a value of 1.0.

[0093]

Number

[0094] Figure 1 shows a two-dimensional plot of the circularity and equivalent circle diameter of the 512 μm sieve particles and the 276 μm sieve particles. As shown in Figure 1(A), the particles in the 512 μm sieve particles had a large equivalent circle diameter and were distributed over a wide range of circularities. In addition, the circularity tended to decrease as the equivalent circle diameter increased. This was presumed to be due to the presence of large particles such as fibrous undecomposed biomass. In contrast, the particles in the 276 μm sieve particles were mostly composed of particles with an equivalent circle diameter of less than 10 μm, as shown in Figure 1(B), and the circularity tended to be high. This was presumed to be due to the fact that most of the small particle size lignin was in the form of aggregates, and the circularity had a high distribution.

[0095] Representative photographs of particles from the 512 μm sieve fraction and the 276 μm sieve fraction are shown in Figure 2. In the figure, X indicates the equivalent circle diameter (μm) and Y indicates the circularity. As shown in Figure 2(A), the particles from the 512 μm sieve fraction consisted of rectangular fibers and many of these fibers were loosened into steel wool-like particles. In contrast, as shown in Figure 2(B), the particles from the 276 μm sieve fraction consisted of particles that had decomposed into fibrous structures, with only lignin remaining, and were aggregated into nearly perfect circles. These results confirmed that when filtering saccharification and fermentation residue in a wet state, it is possible to selectively remove and separate the large-sized fibers shown in Figure 2(A) and selectively leave small-sized substances without fibrous structures shown in Figure 2(B) by using a mesh filter with an opening of 500 μm or less. [Industrial Applicability]

[0096] According to the method for producing a lignin-containing powder of the present embodiment, a lignin-containing powder having a high lignin content and a small particle size, which is useful as a raw material for chemical products, can be prepared from a lignin-containing residue generated during the process of saccharifying or fermenting lignocellulosic biomass. Therefore, the production method and the lignin-containing powder are extremely useful for the effective utilization of lignocellulosic biomass, which is an industrial waste, for example, in the production of biomass ethanol.

Claims

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

2. The method for producing a 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 during the filtration, at least a portion of the deposits on the surface of the filter are peeled off at least once.

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

5. The method for producing a lignin-containing powder according to claim 1, wherein the residue or solution is a saccharification liquid, a fermentation liquid, or a distillation wastewater produced during the saccharification or fermentation of lignocellulosic biomass, or a residue obtained by solid-liquid separation from these.

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

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

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

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

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