JP6177535B2 - Prehydrolyzate treatment system - Google Patents

Description

  The present invention relates to an efficient treatment technique for a prehydrolyzed solution produced by a prehydrolysis treatment in pulp production such as dissolving pulp. In particular, the present invention relates to a technique for producing materials useful per se such as bioethanol, arabinose, methane gas, etc., using a prehydrolyzed liquid, which is a effluent of the prehydrolysis treatment, as a raw material.

  In recent years, studies on effective use of biomass have been actively conducted due to an increase in environmental awareness. Bioethanol produced using biomass as a raw material may be expected to spread further, for example, as an alternative to gasoline. Sugar is produced using lignocellulose such as wood as a biomass raw material, and ethanol is produced by ethanol fermentation. The interest in the technology to obtain is very high.

  In general, the production of bioethanol using lignocellulose as a raw material involves the decomposition of polysaccharides such as cellulose and hemicellulose in lignocellulose into sugars that can be used for fermentation, and the resulting sugars are converted into ethanol by the action of microorganisms and yeasts. Done by converting. However, lignocellulosic raw materials contain lignin and hemicellulose, which can easily inhibit saccharification and alcoholic fermentation (ethanol fermentation) of cellulose. Therefore, the production of bioethanol from lignocellulosic raw materials is extremely It was inefficient and expensive. For this reason, in recent years, bioethanol has become widespread as an energy source to replace gasoline, but the bioethanol used is produced exclusively from cereal raw materials such as corn, wheat, and molasses, which are easily decomposed into monosaccharides. This is the current situation.

  On the other hand, there is a pulp production facility as a large-scale facility that handles lignocellulosic raw materials. In general, a wood pulp manufacturing process has been established on a commercial scale and is known to be a very efficient system.

  In pulp production, pulp mainly composed of cellulose fibers is produced using wood mainly composed of cellulose, hemicellulose, and lignin as raw materials. However, if wastewater discharged in the wood pulp production process can be used effectively, it will be costly. Will be extremely competitive, and will be environmentally superior from the viewpoint of effective use of resources. Wastewater discharged from the wood pulp manufacturing process (pulpation wastewater) contains polysaccharides such as cellulose and hemicellulose, organic substances such as monosaccharides and lignin, and these are used as raw materials to produce bioethanol and the like. It is possible. As a method for producing bioethanol using pulped effluent as a raw material, for example, a system for efficiently producing bioethanol by combining kraft cooking effluent and sulfite cooking effluent has been proposed (Patent Document 1: JP 2009-213389 A). Moreover, although it is not a manufacturing method of bioethanol, about the processing method of the waste_water | drain generate | occur | produced in pulp manufacture, for example, the distillate (KP evadrene) at the time of concentrating the alkaline waste liquid generated from a kraft pulp manufacturing process is processed. Techniques have been proposed (Patent Documents 2 to 3: Japanese Patent Laid-Open Nos. 2009-195852 and 2010-082516). In addition, it has been proposed to treat the liquor cellulosic digestion effluent by methane fermentation (Patent Document 4: Japanese Patent Application Laid-Open No. 2003-213584).

  Further, arabinose is a high value-added material obtained from lignocellulosic materials. As a technology that is practically used to produce arabinose from biomass, a method of hydrolyzing and purifying corn outer skin and cob with a special acid (Patent Document 5: JP-A-11-313700) or beet There is a method of hydrolyzing and purifying pulp with an enzyme (Patent Document 6: Japanese Patent Laid-Open No. 2001-286294). However, in these methods, it is necessary to further hydrolyze the extract obtained from the residue collected from starch and sucrose, and the impurities extracted at the time of decomposition are complicated and diverse. It becomes complicated. As a result, arabinose obtained by these methods is very expensive at present and hinders its spread. As another production method, there is a method of converting glucose with hypochlorous acid, but this method is complicated, and since the produced arabinose is a synthetic product and cannot be said to be a natural product, it is difficult to use for food applications. In some cases (Non-Patent Document 1: J. Am. Chem. Soc., 81, 3136, 1959).

  In addition, in the case of corn, a method of collecting a section having a high Alabama content using a sieve and decomposing it with an acid or an enzyme to obtain an arabinose-containing liquid (Patent Document 7: JP-A-2008-141998), In addition, a method for producing arabinose by hydrolyzing orange fiber, mandarin orange juice, etc. at 70 to 150 ° C. using a mineral acid has been proposed (Patent Document 7: JP 2009-273398 A). In addition, as a technique for producing arabinose using wood as a raw material, it has been studied to separate and purify arabinose from a woody sulfite (sulfurous acid) cooking liquor using a simulated chromatography moving bed (Patent Document 9: Special). Table 2004-533919).

JP 2009-213389 A (Patent No. 5165419) JP 2009-195852 A (Patent No. 5117882) JP 2010-082516 A Japanese Patent Laying-Open No. 2003-213584 (Patent No. 4138319) JP 11-313700 A (Patent No. 3834152) JP 2001-286294 A JP 2008-141998 A (Patent No. 4660457) JP 2009-273398 A JP-T-2004-533919 (Patent No. 4924964)

J. Am. Chem. Soc., 81, 3136, 1959

  The subject of this invention is providing the efficient processing technique of the prehydrolyzed liquid produced in pulp manufacture, such as a dissolving pulp.

  As a result of diligent study, the present inventors applied ethanol fermentation to pre-hydrolyzed liquid (pre-hydrolysis effluent) produced by pre-hydrolysis treatment in pulp production to produce ethanol, It has been found that arabinose can be isolated or purified efficiently, and further, methane gas was obtained by subjecting the remaining treatment liquid to methane fermentation. That is, the prehydrolyzed liquid produced in pulp production contains polysaccharides such as cellulose and hemicellulose, various oligosaccharides and monosaccharides, and further lignin and other organic substances. Based on the present invention, ethanol fermentation treatment, arabinose By combining the separation process and the methane fermentation process, it is possible to efficiently produce useful materials such as bioethanol, arabinose, and methane gas using the substances contained in the prehydrolyzed liquid as raw materials.

  The present invention can be evaluated from a variety of viewpoints from various viewpoints. If attention is paid to the treatment target (treatment raw material) of the present invention, it can be grasped as a treatment method for a prehydrolyzed liquid produced in pulp production. If attention is paid to the processed product (processed product) obtained from the present invention, it can be evaluated as bioethanol production technology, arabinose production technology, methane gas production technology, and heat energy recovery technology.

Although not limited to this, this invention includes invention of the following aspects.
(1) A step of obtaining a bioethanol and a treatment liquid by ethanol fermentation of a prehydrolyzed liquid produced by pre-hydrolysis of wood during pulp production, a step of taking out arabinose from the treated liquid after ethanol fermentation, and after taking out arabinose A method for treating a prehydrolyzed liquid produced in pulp production, comprising a step of methane fermentation of the treated liquid to obtain methane gas and methane fermentation effluent.
(2) The method according to (1), wherein the prehydrolyzed liquid is a prehydrolyzed liquid produced by prehydrolysis of softwood.
(3) The method according to (1) or (2), wherein the prehydrolyzed liquid is a prehydrolyzed liquid produced in kraft pulp production.
(4) The method according to any one of (1) to (3), wherein ethanol fermentation is performed with yeast.
(5) A step of obtaining a bioethanol and a treatment liquid by ethanol fermentation of a prehydrolyzed liquid produced by pre-hydrolysis of wood during pulp production, a step of taking out arabinose from the treated liquid after ethanol fermentation, A process for producing bioethanol from a pre-hydrolyzed liquid produced in pulp production, comprising the step of methane fermentation of the treated liquid to obtain methane gas and methane fermentation effluent.
(6) Step of obtaining bioethanol and a treatment liquid by ethanol fermentation of a prehydrolyzed liquid produced by wood pre-hydrolysis during pulp production, Step of taking out arabinose from the treated liquid after ethanol fermentation, After taking out arabinose A process for producing arabinose from a pre-hydrolyzed liquid produced in pulp production, comprising the step of methane fermentation of a treated liquid of methane to obtain methane gas and methane fermentation effluent.
(7) A step of obtaining a bioethanol and a treatment liquid by ethanol fermentation of a prehydrolyzed liquid produced by prehydrolysis of wood during pulp production, a step of taking arabinose from the treatment liquid after ethanol fermentation, and after taking out arabinose A process for producing methane gas from a prehydrolyzed liquid produced in pulp production, comprising the step of methane fermentation of a methane fermentation liquid to obtain methane gas and methane fermentation effluent.

  ADVANTAGE OF THE INVENTION According to this invention, the efficient processing technique of the prehydrolyzed liquid produced in pulp manufacture is provided. In particular, according to the present invention, it is possible to effectively utilize the prehydrolyzed liquid that is the waste liquid of the prehydrolysis treatment, and to produce useful substances such as bioethanol, arabinose, and methane gas, as well as to realize thermal energy recovery. Is possible. Further, according to the present invention, it is possible to stably treat a pre-hydrolyzed liquid that contains a large amount of organic matter and cannot be discharged to the environment as it is, and lower COD and the like. Furthermore, according to the present invention, biomass can be effectively used comprehensively, and the present invention has an extremely high social contribution from an environmental point of view.

FIG. 1 is a schematic view showing an embodiment of the processing system of the present invention. FIG. 2 is a schematic diagram showing one embodiment of the processing system of the present invention. FIG. 3 is a schematic diagram showing one embodiment of the processing system of the present invention. FIG. 4 is a schematic diagram showing one embodiment of the processing system of the present invention. FIG. 5 is a schematic view showing an aspect of the processing system of the present invention.

Prehydrolyzed liquid produced in pulp production The subject of the present invention is a prehydrolyzed liquid produced in pulp production. In general, pulp is produced by digesting wood. However, when producing a pulp having a high cellulose content such as dissolved pulp, wood as a raw material is pretreated with high-temperature water or steam. Since hemicellulose contained in wood is hydrolyzed by this pretreatment, hemicellulose can be efficiently removed, and a pulp having high cellulose purity is produced by digesting the prehydrolyzed treatment. Can do. This pre-treatment is called pre-hydrolysis treatment, and the drainage produced by the pre-hydrolysis treatment is called pre-hydrolysis liquid.

  As described above, when producing pulp having a high cellulose content such as dissolved pulp, the wood chips are prehydrolyzed and then cooked by sulfite cooking method (SP method) or kraft cooking method (KP method). Is performed to produce pulp. Specifically, solid-liquid separation (separation) is performed after the prehydrolysis treatment, and the wood fibers that are solid components are made into raw materials for pulp production by cooking, while the drainage produced by the prehydrolysis treatment ( No effective utilization method has been found for the prehydrolyzed liquid.

  As for the treatment and utilization of such a prehydrolyzed liquid, the production of dissolving pulp in Japan has not been so large so far, and a full-scale examination has not been made. However, since the waste liquid discharged by prehydrolysis (prehydrolyzed liquid) contains a large amount of organic substances, COD (chemical oxygen demand) and BOD (biochemical oxygen demand) are extremely high and are directly in the environment. Although it cannot be released, it would be extremely advantageous if it could be used as a resource.

  The treatment target of the present invention is a prehydrolyzed liquid produced in pulp production, and in particular, a prehydrolyzed liquid produced in the production of dissolving pulp (DP) and a prehydrolyzed liquid produced in the production of kraft pulp (KP) are preferable. It is an object to be processed, and in a certain aspect, a pre-hydrolyzed liquid produced when manufacturing dissolved kraft pulp (DKP) can be an object to be processed. In the pre-hydrolysis treatment in pulp production, the wood is hydrolyzed using high-temperature water to reduce the hemicellulose in the wood, breaking the bond between hemicellulose and cellulose, and the hemicellulose content in the wood chips. Is decomposed into water-soluble sugars, the pre-hydrolyzed solution contains a large amount of organic substances such as sugars and lignin. Therefore, the prehydrolyzed liquid contains hemicelluloses such as xylan and glucomannan separated from cellulose, and monosaccharides produced by the decomposition of hemicellulose.

  The prehydrolyzed liquid used in the present invention is not particularly limited to the wood to be prehydrolyzed, and coniferous trees and / or hardwoods can be used. Examples of coniferous trees are spruce, todomatsu, red pine, black pine, larch, cedar, cypress, western larch, radiata pine, black spruce, white spruce, western hemlock, southern pine, balsam fur, larch, jack pine, douglas fir, etc. Can be mentioned. As an example of a broad-leaved tree, Eucalyptus wood can be mentioned as a suitable example. The pre-hydrolyzed liquid of the present invention is a waste liquid generated by the pre-hydrolysis of chips mixed with two or more kinds of wood, even if it is drained by the pre-hydrolysis of a single type of wood chips. Also good. Moreover, the production area in particular of wood is not restrict | limited, You may be from Japan or foreign. Larch, red pine, cedar, eucalyptus, etc. are suitable for the practice of the present invention.

  In a preferred embodiment of the present invention, a prehydrolyzed solution obtained when a softwood material is prehydrolyzed can be used. Since conifers generally contain hemicellulose containing a relatively large amount of arabinose, prehydrolyzed effluent obtained by prehydrolyzing coniferous wood is preferable from the viewpoint of producing arabinose. Examples of preferable coniferous materials include larch, red pine, cedar and the like.

  Conventionally, the wood of the genus Pinus has been known as a wood rich in hemicellulose containing arabinose in the side chain, but its content is less than that of corn hulls or beet pulp. In addition, it is technically difficult to extract arabinose from woods compared to herbs, and since acid hydrolysis of wood entails a large amount of glucose and wood extract components, Little consideration has been given to wood as a raw material. According to the present invention, arabinose can be efficiently obtained from wood. The reason is not limited to this, but is estimated as follows. That is, compared to corn and other woody biomass, softwood and other wood contain more arabinogalactans with arabinose in the side chain, and in particular, all these arabinogalactans have side chain ends. It is presumed that it is easily hydrolyzed because it is bound in an exposed form (Yoji Kato et al., “Plant cell wall and polysaccharides” Baifukan). Therefore, it is considered that arabinose can be efficiently produced by using a pre-hydrolyzed liquid of wood as a raw material as in the present invention.

  When obtaining the prehydrolysis liquid of this invention, it is preferable to use the wood used for a prehydrolysis process below to a certain size. That is, when wood is used in chips or powders, the prehydrolysis treatment can be carried out efficiently, so that it is possible to obtain a prehydrolyzed solution rich in raw materials for ethanol fermentation and methane fermentation and arabinose. it can. The size of the wood may be a size generally used for pulp and papermaking (for example, a length of 15 to 20 mm in the grain direction, a width of 12 to 25 mm, a thickness of about 10 mm or less), and penetrates hot water. One side can be 3-6 mm in size to facilitate extraction and increase hydrolysis efficiency.

  In the present invention, the conditions for the prehydrolysis treatment applied to the wood are not particularly limited, and the prehydrolysis can be performed under known conditions. For example, when pre-hydrolyzing wood such as coniferous wood by hydrothermal treatment, the wood can be treated with high-temperature and high-pressure water under conditions of 150 to 450 ° C. and 1.0 to 100 MPa. As for the temperature of the hot water in the hydrothermal reaction of prehydrolysis, 160-300 degreeC is more preferable, and 165-250 degreeC is further more preferable. If the temperature of hot water is too low, hydrolysis efficiency may decrease and oligosaccharides may increase too much, while if the temperature of hot water is too high, excessive decomposition will proceed and yield of arabinose will decrease. There is.

  Any water may be used in the pre-hydrolysis of the present invention, but water having a lower hardness can provide a better extraction / hydrolysis effect. The range of hardness is not particularly limited, but is preferably 100 or less, and more preferably 50 or less.

  The amount of water relative to the wood that is the raw material is preferably such that the ratio (liquid ratio) of water to the absolute dry weight of wood is in the range of 1 to 10, from the viewpoint of increasing the sugar concentration contained in the prehydrolyzed liquid, 2 to 5 is more preferable, and 2.5 to 3.5 is particularly suitable. If the liquid ratio is too low, efficient extraction is difficult, and if the liquid ratio is too high, the concentration of the extract becomes thin, which is disadvantageous in the subsequent steps.

  The treatment time of the hydrothermal reaction in the prehydrolysis is not particularly limited, but is preferably 15 minutes to 10 hours, more preferably 30 minutes to 5 hours, and further preferably 30 minutes to 3 hours. Although it varies slightly depending on the difference between the batch type and the continuous type, the heating time, etc., the treatment time as described above can sufficiently carry out the hydrolysis reaction itself, and the pre-hydration suitable for the present invention. A decomposition solution can be obtained.

  The pH of the prehydrolyzed liquid used in the present invention is not particularly limited, but the pH is often about 2 to 7 depending on the acid generated by the hydrolysis of wood, and in some embodiments the pH is about 2 to 6 or 3 to 4 May be.

Ethanol Fermentation In the present invention, ethanol fermentation (alcohol fermentation) is first performed using a prehydrolyzed solution produced in pulp production. In general, the production of bioethanol using lignocellulose such as wood as a raw material decomposes polysaccharides such as cellulose and hemicellulose in lignocellulose into sugars that can be used for fermentation, and the resulting sugars are used by microorganisms and yeasts. By conversion to ethanol. In the present invention, the sugar contained in the prehydrolyzed solution is used as a raw material for ethanol fermentation to obtain ethanol.

  Ethanol fermentation is a metabolic process that obtains energy by decomposing sugars such as glucose, fructose, and sucrose to produce ethanol and carbon dioxide. Ethanol fermentation is an anaerobic reaction that basically does not require oxygen, and in the present invention, the sugar contained in the prehydrolyzed solution is ethanol fermented to obtain ethanol and a fermented solution (treatment solution).

  In the present invention, ethanol obtained as a result of ethanol fermentation is bioethanol produced from wood, which is a biomass resource. In recent years, bioethanol has been taken up as an important solution to the energy problem and is becoming popular as an energy source to replace gasoline. However, the bioethanol used is easily decomposed into monosaccharides such as corn, wheat and waste. It is generally made from cereal raw materials such as molasses. However, according to the present invention, it is possible to efficiently produce bioethanol from wood raw materials.

  In ethanol fermentation, the sugar in the prehydrolyzed liquid is converted to ethanol by the activity of microorganisms and yeast. Yeast is a typical organism that undergoes alcoholic fermentation using sugar in the absence of oxygen, and is widely used in the production of foods such as alcoholic beverages and bread in addition to the production of bioethanol. In addition, ethanol fermentation without yeast is a reaction called “carbonic maceration”, an anaerobic reaction that occurs in the fruits of grapes placed in high concentrations of carbon dioxide or nitrogen gas (low oxygen atmosphere). And sugar is changed into alcohol by the action of the enzyme. This technique is used in brewing alcoholic beverages such as wine.

  In the present invention, when yeast is used for ethanol fermentation of a prehydrolyzed solution, conventionally used yeasts can be used without limitation, for example, Saccharomyces cereviseae, as well as gene Strains that have been engineered to have pentose utilization and fermentation ability and yeasts having ethanol fermentation ability such as C. krusei can be preferably used. In addition, as microorganisms, E.coli strains with ethanol fermentation ability were genetically engineered, Z.mobilis, strains that were genetically engineered with pentose utilization ability, C. glutamicum, and mutants thereof. However, any microorganism can be used as long as it is capable of ethanol fermentation, and a microorganism suitable for the properties, composition, fermentation conditions, etc. of the pre-hydrolyzed liquid as a raw material may be selected. In ethanol fermentation, it is also preferable to add a nutrient source such as ammonia, ammonia phosphate, or urea.

  In the present invention, the conditions for ethanol fermentation are not particularly limited and can be appropriately set according to the conditions, and a known ethanol fermentation apparatus can be used.

  In a preferred embodiment of the present invention, bioethanol obtained by ethanol fermentation can be distilled and purified. That is, the system of the present invention can include an ethanol distillation apparatus and a purification apparatus.

  The bioethanol thus obtained can be used as an energy source and can be sold as it is, or can be consumed as an energy source in the present system.

Pretreatment of prehydrolyzed liquid In the present invention, ethanol fermentation is performed using a prehydrolyzed liquid, but the prehydrolyzed liquid can also be pretreated in order to more efficiently perform ethanol fermentation. As already mentioned, since the prehydrolyzed liquid also contains cellulose, hemicellulose, polysaccharides, oligosaccharides, etc., the polysaccharides contained in the prehydrolyzed liquid are further hydrolyzed and subjected to ethanol fermentation. It is preferable to remove a component unnecessary for ethanol fermentation or a component that inhibits ethanol fermentation by increasing the concentration of sugar as a material or by performing a known separation and purification treatment. Moreover, in a preferable aspect, you may provide the process of collect | recovering the useful components contained in a prehydrolysis liquid before ethanol fermentation.

  Specifically, before ethanol-fermenting the pre-hydrolyzed solution, hydrolysis treatment can be performed using an acid or an enzyme to increase the concentration of sugar that is a raw material for ethanol fermentation. In general, the methods for degrading polysaccharides such as cellulose and hemicellulose into sugars are: (1) acid saccharification using mineral acid, and (2) enzyme saccharification using an enzyme or a microorganism that produces the enzyme. Broadly divided into laws. Furthermore, in the acid saccharification method, concentrated sulfuric acid or dilute sulfuric acid is often used as a mineral acid, which are called concentrated sulfuric acid method and dilute sulfuric acid method, respectively. In the present invention, any method can be used for pretreatment of the prehydrolyzed liquid.

  In a method using an acid such as a concentrated sulfuric acid method or a dilute sulfuric acid method, hydrolysis of lignocellulose proceeds relatively easily, and the resulting glucose derived from glucose is subjected to ethanol fermentation. In the case of a method using a weak acid such as dilute sulfuric acid method, pretreatment of the prehydrolyzed solution in a plurality of steps is preferable because the glucose concentration can be improved efficiently. As for hydrolysis using an acid, for example, a method described in US Pat. No. 5,424,417 and JP-A-2005-229821, a method using concentrated sulfuric acid (JP-A-2005-229822), pressurized hot water, and the like. (Japanese Patent Laid-Open No. 2007-20555) has been proposed, and these methods can also be applied in the present invention. In addition, if the pretreatment of the prehydrolyzed liquid is excessive, the generated sugar may be changed to an ethanol fermentation inhibitor such as furfural or tar, so it may be better to optimize the treatment conditions. (Wood and Fiber Science, April, 1986, Vol.18 (2) P248-263).

  When the prehydrolyzed liquid is treated with an enzyme, the enzyme used is not particularly limited as long as it can saccharify cellulose or hemicellulose, but it can be preferably used as long as it is a cellulase capable of degrading cellulose to glucose. Some enzymes are preferred. From the viewpoint of degradation activity, it is desirable to use an enzyme having a balanced degradation activity of endo-glucanase, exo-glucanase, and β-glucosidase. For example, NS50013, NS50010 and Ctec2 which are cellulases manufactured by Novo Corporation, Optimash BG of Genencor Kyowa Co., Axelase, Sumiteam AC of Shinnippon Chemical Co., Ltd., etc. can be preferably used. It is not something.

  In addition, the prehydrolyzed liquid may be pretreated, and components unnecessary for ethanol fermentation, components that inhibit ethanol fermentation, or useful components contained in the prehydrolyzed liquid may be recovered in advance from the prehydrolyzed liquid. In a preferred embodiment, substances such as mannans can be separated from the prehydrolyzed solution using, for example, separation / purification means such as membrane separation.

  Furthermore, it is also possible to implement both a hydrolysis process and a separation purification process as a pretreatment applied to the prehydrolyzed liquid. For example, after partial degradation of hemicellulose, etc. contained in the prehydrolyzed solution to the oligosaccharide by hydrolysis using an enzyme, the partially hydrolyzed prehydrolyzed solution is subjected to separation and purification treatment, oligosaccharide, etc. It is also possible to obtain useful substances.

Separation of arabinose In the present invention, arabinose can be obtained using a treatment liquid after ethanol fermentation of the prehydrolyzed liquid. As already mentioned, the prehydrolyzed liquid produced in pulp production contains various organic substances such as various sugars and lignin in addition to arabinose. Prehydrolyzed by subjecting the prehydrolyzed liquid to ethanol fermentation. Monosaccharides and oligosaccharides contained in the liquid are consumed, and it becomes easy to separate arabinose from the treatment liquid after ethanol fermentation. That is, by using a treatment liquid obtained by ethanol fermentation of the prehydrolyzed liquid as in the present invention, arabinose can be obtained much more efficiently than when separating and purifying arabinose directly from the prehydrolyzed liquid. . For example, when Saccharomyces yeast is used during ethanol fermentation, hexoses such as glucose, mannose, and arabinose contained in the prehydrolyzed solution are basically consumed, but arabinose is not consumed, so arabinose is isolated after ethanol fermentation. By purifying, arabinose can be obtained efficiently.

  As a method for separating and purifying arabinose from the treatment liquid after ethanol fermentation of the present invention, a known method can be used without limitation. For example, after filtration and concentration, arabinose is separated by chromatography, and the separated liquid may be further purified by chromatography or the like. As the filtration method, diatomaceous earth filtration, filter paper filtration, microfiltration and other filtration treatments can be used alone or in combination. Examples of the concentration method include heating, reduced pressure, reduced pressure heating, and ultrafiltration. As the chromatography, chromatography using an ion exchange resin as a filler, simulated moving bed chromatography, and other chromatography are used. Further, if necessary, it may be concentrated after removing the colored components by activated carbon or the like according to a conventional method, and cooled and crystallized.

  Arabinose is an indigestible non-caloric pentose sugar and has 60% sweetness of sucrose. In recent years, it has been found that arabinose inhibits sucrose-degrading enzyme in the small intestine to suppress the increase in blood sugar level and insulin during sucrose intake, and also has a second-meal effect that continues to be effective, Attention has been paid. As already mentioned, arabinose currently on the market is very expensive. However, according to the present invention, arabinose can be produced using waste liquid produced in pulp production as a raw material, which is extremely advantageous.

  Moreover, when importance is attached to the yield of arabinose, it is preferable that the prehydrolysis liquid used by this invention is a prehydrolysis liquid discharged | emitted when pre-hydrolyzing a conifer. This is because conifers among wood are rich in hemicellulose containing arabinose in its structure. As the conifer, larch is particularly preferable.

Methane fermentation In the present invention, the prehydrolyzed solution is ethanol-fermented to separate arabinose, and the resulting treatment solution is further subjected to methane fermentation. The prehydrolyzed liquid discharged by the prehydrolysis of wood contains a large amount of hemicellulose hydrolyzate, but also contains abundant organic substances such as lignin contained in wood. Therefore, the treatment liquid after performing ethanol fermentation contains a lot of organic substances that were not used for ethanol fermentation, and methane gas can be efficiently obtained by performing methane fermentation using such organic substances as raw materials. Can do.

  In the present invention, methane fermentation is generally called anaerobic treatment, and decomposes organic components in wastewater into methane and carbon dioxide using anaerobic microorganisms such as acid-producing bacteria and methane bacteria under anaerobic conditions. Biological treatment method. Since methane fermentation does not require aeration energy and generates a small amount of sludge, the environmental load is small, and the generated methane gas can be effectively used as fuel.

  The conditions for the anaerobic treatment of the present invention are not particularly limited, and so-called medium temperature methods and high temperature methods can be suitably applied. Since energy consumption is low, the anaerobic treatment of the present invention is an intermediate temperature method in a preferred embodiment, and the treatment temperature is preferably 30 to 45 ° C, more preferably 30 to 37 ° C.

  In the present invention, the pH during the anaerobic treatment is preferably 6.0 to 8.5, more preferably 7.0 to 8.0. This is because the optimum region of anaerobic microorganisms is usually near neutrality. You may adjust the pH of a process liquid as needed.

  In the anaerobic treatment of the present invention, the contact time with the anaerobic microorganism is not particularly limited, but is preferably 4 hours to 60 days, more preferably 1 day to 30 days, and more preferably 2 days to 15 days. More preferably, days.

  The anaerobic treatment of the present invention may be performed in one reaction tank or a plurality of reaction tanks. However, according to the treatment method of the present invention, a stable anaerobic treatment is possible, so that one tank is used. Even in the anaerobic treatment of the system, methane fermentation can be performed efficiently. The anaerobic state can be managed by ORP (oxidation reduction potential) or the like.

  There is no particular limitation on the anaerobic microorganisms used in the anaerobic treatment of the present invention, and general ones can be used, but self-aggregated pellets called granule sludge can be suitably used. Examples of methane bacteria include methanol-degrading bacteria (Methanosarcina) and acetic acid-degrading bacteria (Methanosaeta).

  In addition, in the present invention, an additional step can be added in addition to the anaerobic treatment step as long as the characteristics of the present invention are not impaired. Can be added. For example, anaerobic treatment can be combined with the anaerobic treatment according to the present invention.

  In the present invention, a suitable pretreatment can be applied to the treatment liquid used for methane fermentation. For example, relatively large foreign matter may be removed by screen treatment or the like.

  The waste liquid after methane fermentation according to the present invention may be discharged into the environment such as the ocean or river, and may be reused as factory water.

  Furthermore, in order to perform the method according to the present invention under optimum conditions, the present invention can include a control step of adjusting the balance with other steps. For example, when the present invention and the energy recovery process using biogas obtained by the present invention are operated as one system, it is possible to optimally control the entire system by adopting, for example, feedback control as a control method. is there.

  Although the product of the methane fermentation of the present invention is mainly methane gas, the methane gas can be used as an energy source in the pulp mill, or the biogas itself can be used for other applications. When the biogas obtained by the present invention is used as an energy source, it is preferable to use it in the same factory from the viewpoint of transportation cost. Typically, the biogas according to the present invention is a recovery boiler as a good quality fuel. And can be used in kilns.

Manufacturing Flow Hereinafter, the present invention will be described with specific preferred embodiments.

  FIG. 1 is a schematic diagram illustrating one preferred embodiment of the system of the present invention. In this embodiment, the step of subjecting the prehydrolyzed solution to ethanol fermentation to obtain ethanol and a fermented solution (treatment solution), the step of separating and taking out arabinose from the treatment solution, and then subjecting the remaining treatment solution to methane fermentation and methane gas And a step of obtaining drainage.

  In this embodiment, since the ethanol fermentation is performed without any pretreatment on the prehydrolyzed liquid, the process and apparatus can be made relatively simple. In the present invention, ethanol fermentation may be performed in one stage or in multiple stages. Furthermore, ethanol (crude ethanol) obtained by ethanol fermentation may be purified by a purification apparatus. The pH in ethanol fermentation is not particularly limited, but it is preferable to perform ethanol fermentation in an acidic region to a neutral region in accordance with the characteristics of the yeast to be used.

  The treatment liquid after mainly consuming monosaccharides by ethanol fermentation mainly contains arabinose, lignin sulfonic acid, etc. In this embodiment, it is a useful substance from the treatment liquid using chromatography or the like. Take out arabinose. Thereafter, the remaining treatment liquid is subjected to methane fermentation to generate methane gas. The drainage finally obtained has a significantly reduced organic content compared to the pre-hydrolyzed liquid to be treated, and can be released into the environment.

  FIG. 2 is a schematic diagram illustrating one preferred embodiment of the system of the present invention. In this embodiment, the prehydrolyzed solution is further hydrolyzed with an acid. In this embodiment, all or part of cellulose or hemicellulose contained in the prehydrolyzed liquid can be converted into a fermentable sugar liquid by acid hydrolysis, so that bioethanol can be more efficiently obtained by subsequent ethanol fermentation. Can be obtained.

  FIG. 3 is a schematic diagram illustrating one preferred embodiment of the system of the present invention. In this embodiment, before the prehydrolyzed solution is ethanol-fermented, the prehydrolyzed solution is further hydrolyzed using an enzyme. In this embodiment, all or a part of cellulose or hemicellulose contained in the prehydrolyzed liquid can be converted into a fermentable sugar solution by enzymatic decomposition with a cellulolytic enzyme or hemicellulose degrading enzyme. Bioethanol can be obtained more efficiently.

  FIG. 4 is a schematic diagram illustrating one preferred embodiment of the system of the present invention. In this embodiment, before the prehydrolyzed solution is ethanol-fermented, the prehydrolyzed solution is further hydrolyzed using an enzyme. In this embodiment, all or part of cellulose or hemicellulose contained in the prehydrolyzed solution is enzymatically decomposed by cellulose-degrading enzyme or hemicellulose-degrading enzyme, but it is not always necessary to decompose all of them to monosaccharides. It may be a decomposition to a state where oligosaccharides or monosaccharides are mixed. In this aspect, for example, after the prehydrolysis solution is enzymatically decomposed, the oligosaccharide that is a useful substance can be extracted from the prehydrolysis solution by performing a treatment such as removing the oligosaccharide contained in the treatment solution. At the same time, subsequent ethanol fermentation can be carried out efficiently.

  FIG. 5 is a schematic diagram illustrating one preferred embodiment of the system of the present invention. In this embodiment, before ethanol-fermenting the prehydrolyzed liquid, a step of taking out mannans which are useful substances from the prehydrolyzed liquid by a separation treatment is included. By pretreating the prehydrolyzed liquid in this way, useful substances can be taken out from the prehydrolysis, and subsequent ethanol fermentation can be efficiently performed.

Claims (7)

A step of pre-hydrolyzing wood with water such that the ratio (liquid ratio) of water to the absolute dry weight of wood is 1 to 5 during the production of dissolved kraft pulp ;
A step of ethanol-fermenting a prehydrolyzed solution produced by prehydrolysis to obtain bioethanol and a treatment solution;
A process of taking arabinose from the treatment liquid after ethanol fermentation,
A process of obtaining methane gas and methane fermentation effluent by methane fermentation of the treatment liquid after taking out arabinose,
A method for treating a prehydrolyzed liquid produced in the production of dissolved kraft pulp. The method according to claim 1, further comprising the step of further hydrolyzing the prehydrolyzed liquid using an enzyme. The method according to claim 1 or 2 , wherein the prehydrolyzed liquid is a prehydrolyzed liquid produced by prehydrolysis of softwood.   The method in any one of Claims 1-3 which performs ethanol fermentation by yeast. A step of pre-hydrolyzing wood with water such that the ratio (liquid ratio) of water to the absolute dry weight of wood is 1 to 5 during the production of dissolved kraft pulp ;
A process of obtaining bioethanol and a treatment liquid by ethanol fermentation of a prehydrolyzed liquid produced by prehydrolysis of wood,
A process of taking arabinose from the treatment liquid after ethanol fermentation,
A process of obtaining methane gas and methane fermentation effluent by methane fermentation of the treatment liquid after taking out arabinose,
A process for producing bioethanol from a prehydrolyzed liquid produced in the production of dissolved kraft pulp. A step of pre-hydrolyzing wood with water such that the ratio (liquid ratio) of water to the absolute dry weight of wood is 1 to 5 during the production of dissolved kraft pulp ;
A process of obtaining bioethanol and a treatment liquid by ethanol fermentation of a prehydrolyzed liquid produced by prehydrolysis of wood,
A process of taking arabinose from the treatment liquid after ethanol fermentation,
A process of obtaining methane gas and methane fermentation effluent by methane fermentation of the treatment liquid after taking out arabinose,
A process for producing arabinose from a prehydrolyzed liquid produced in the production of dissolved kraft pulp. A step of pre-hydrolyzing wood with water such that the ratio (liquid ratio) of water to the absolute dry weight of wood is 1 to 5 during the production of dissolved kraft pulp ;
A process of obtaining bioethanol and a treatment liquid by ethanol fermentation of a prehydrolyzed liquid produced by prehydrolysis of wood,
A process of taking arabinose from the treatment liquid after ethanol fermentation,
A process of obtaining methane gas and methane fermentation effluent by methane fermentation of the treatment liquid after taking out arabinose,
A process for producing methane gas from a prehydrolyzed liquid produced in the production of dissolved kraft pulp.

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