JP2011045277A - Production system for cellulose-based ethanol, and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system and method for producing cellulose-based ethanol by using a lignocellulose raw material capable of suppressing the concentration energy of fermented ethanol without reducing the efficiency of saccharification reaction. <P>SOLUTION: This production system for cellulose-based ethanol for producing ethanol by using the lignocellulose as the raw material is characterized by comprising a saccharification means for converting the lignocellulose into saccharides by using an enzyme, a saccharide liquid-concentrating means for concentrating the saccharide liquid obtained by the saccharification means, a fermenting means for ethanol-fermenting the concentrated saccharide liquid by using an yeast, and a means for separating and purifying the ethanol from the ethanol fermentation liquid obtained by the fermenting means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a production system and a production method for cellulosic ethanol using lignocellulose as a raw material.

  In recent years, global bioethanol production has been promoted globally as a countermeasure against global warming. In terms of bioethanol production, ethanol is mainly made from edible biomass such as corn and sugarcane, but there is a demand for the popularization of ethanol production from lignocellulose such as wood and grass that does not compete with food. . In ethanol production from lignocellulose, it is particularly desired to use agricultural residues such as rice straw, lignocellulose such as stovers (leaf stems of corn), herbs, and the like.

  In order to produce ethanol from lignocellulose derived from biomass such as wood and grass (forestry residues, waste materials, agricultural residues, fishery residues, etc.), the cellulose and hemicellulose in lignocellulose are first hydrolyzed using saccharifying enzymes. Then, it is converted to free sugar or oligosaccharide (saccharification), and then the free sugar or oligosaccharide is fermented and converted to ethanol, and ethanol is recovered from the obtained fermentation broth and purified to a predetermined quality.

  Here, a pretreatment is required to cause saccharification enzyme to act on lignocellulose. As such a pretreatment technique, an acid treatment method, a steam explosion method, a mechanical grinding method, and the like are known. In the method using an acid such as dilute sulfuric acid for pretreatment, the efficiency as a saccharification system is lowered because a large-scale treatment step is required for neutralization and recovery of the acid. Patent Document 1 proposes a cellulose treatment method in which lignocellulose is processed by a pulverizer following hot water treatment to efficiently produce saccharides by enzymatic saccharification.

  In addition, the distillation method has generally been used for concentration and dehydration of fermented ethanol, but it is known that the energy consumed for ethanol separation is about half of the calorific value of ethanol. Development of an introduced high-efficiency ethanol concentration / dehydration method has been carried out (for example, see Non-Patent Document 1).

  By the way, in ethanol production using a cellulosic raw material such as lignocellulose, the concentration of the sugar solution obtained by enzymatic saccharification is generally as low as 3 to 5%, and accordingly, the concentration of fermented ethanol is generally 3% or less, Compared to ethanol production from molasses and starch, the energy consumed in the concentration process of fermented ethanol is excessive. As a method for coping with this, Non-Patent Document 2 proposes a method for increasing the concentration of fermented ethanol obtained by saccharification / fermentation by introducing a process of concentrating lignocellulose stock solution before the enzymatic saccharification process. However, in this method, since the sugar concentration in the enzymatic saccharification process is high, there is a possibility that the progress of the saccharification reaction is slowed down and a side effect of reducing the saccharification yield may occur.

JP 2006-136263 A

H. Iwasaki, etc., Improvement of the Refinement Process for Bioethanol, Journal of the Japan Institute of Energy, 84, pp.852-860, 2005 S. Fujimoto, etc., Bioethanol Production from Lignocellulosic Biomass Requiring No Sulfuric Acid: Mechanochemical Pretreatment and Enzymic Saccharification, Journal of the Japan Petroleum Institute, 51-5, pp.264-273, 2008

  Therefore, the present invention provides a cellulose-based ethanol production system capable of suppressing energy consumption in a fermentation ethanol concentration process without reducing the efficiency of a saccharification reaction in the production of cellulose-based ethanol using a lignocellulose raw material. The purpose is to provide a production method.

The cellulosic ethanol production system of the present invention is a cellulosic ethanol production system for producing ethanol using lignocellulose as a raw material,
A saccharification means for converting lignocellulose into sugar using an enzyme, a sugar liquid concentration means for concentrating the sugar liquid obtained by the saccharification means, and a fermentation means for subjecting the concentrated sugar liquid to ethanol fermentation using yeast. And means for separating and purifying ethanol from the ethanol fermentation liquid obtained by the fermentation means.
The cellulose-based ethanol production method of the present invention is a cellulose-based ethanol production method for producing ethanol using lignocellulose as a raw material,
A saccharification step for converting lignocellulose to sugar using an enzyme, a saccharide solution concentration step for concentrating the saccharide solution obtained by the saccharification step, and a fermentation step for ethanol fermentation of the concentrated saccharide solution using yeast. And a step of separating and purifying ethanol from the ethanol fermentation liquid obtained by the fermentation step.

  According to the cellulose-based ethanol production system and production method of the present invention, in the production of cellulose-based ethanol using a lignocellulose raw material, energy consumption in the fermentation ethanol concentration process is suppressed without reducing the efficiency of the saccharification reaction. Is possible.

It is a flowchart which shows one Embodiment of the cellulose ethanol production system which concerns on this invention. It is a flowchart which shows another embodiment of the cellulosic ethanol production system which concerns on this invention. It is a figure explaining the separation method of ash by a residue classifier. It is a figure which shows the structure of the cellulosic ethanol production system in Example 1. FIG. It is a figure which shows the structure of the cellulose ethanol production system in Example 2. FIG.

  Hereinafter, an embodiment of a cellulosic ethanol production system according to the present invention will be described.

  The cellulose-based ethanol production system of the present invention is a cellulose-based ethanol production system that produces ethanol using lignocellulose as a raw material, and has the following means (A) to (D) in order.

(A) Lignocellulose saccharification means by enzyme (B) Sugar liquid concentration means for concentrating sugar liquid (C) Ethanol fermentation means by yeast of concentrated sugar liquid (D) Separation and purification means from ethanol fermentation liquid

  In the cellulosic ethanol production system of the present invention, (B) saccharification means is provided after (A) saccharification means, and the saccharification is performed here, thereby affecting the saccharification reaction of (A) saccharification means. (D) The ethanol separation and purification means provided thereafter can reduce energy consumption related to the separation and purification of ethanol. This can be expected to save energy in the whole cellulosic ethanol production system.

As a lignocellulose raw material to which the cellulose-based ethanol production system of the present invention is applied, any material containing lignocellulose can be used without particular limitation, whether it is woody biomass or herbaceous biomass. .
Lignocellulose is a component that constitutes the cell wall of plants, and is composed mainly of polysaccharide cellulose and hemicellulose, and aromatic polymer lignin, and has a complex structure in which crystalline cellulose is surrounded by hemicellulose and lignin. It is. In such a structure, the saccharification reaction of cellulose and hemicellulose cannot be performed efficiently. Therefore, when saccharifying lignocellulose, a pretreatment for separating cellulose and hemicellulose from lignin is generally performed. Here, in lignocellulose derived from woody biomass and lignocellulose derived from herbaceous biomass, woodic lignocellulose has a higher lignin content, so before it is provided before the above (A) saccharification means There are differences in the means for processing. The following means (A) to (D) can be the same means regardless of whether they are woody or herbaceous.
Hereinafter, embodiments of the cellulosic ethanol production system of the present invention will be described with reference to the drawings, divided into woody and herbaceous systems.

  FIG. 1 is a flowchart showing an embodiment of a cellulosic ethanol production system according to the present invention. This embodiment is a preferred embodiment when a woody lignocellulose raw material is used. FIG. 2 is a flowchart showing another embodiment of the cellulosic ethanol production system according to the present invention. This embodiment is suitable when a herbaceous lignocellulose raw material is used.

  An embodiment of the cellulosic ethanol production system according to the present invention using the woody lignocellulose raw material shown in FIG. 1 will be described. The woody lignocellulose raw material to be used is not particularly limited as long as it is woody biomass.

(Means related to pretreatment)
In the case of using a woody lignocellulose raw material in the cellulose ethanol production system according to the present invention, (A) as a pretreatment means before the saccharification means, as shown in FIG. It is preferable to provide means for performing each of the pulverization processes.
The coarse pulverization process is a process in which the lignocellulose raw material is coarsely pulverized in advance to a size of several mm in order to increase the speed of each process performed thereafter. Specifically, this coarse pulverization treatment can be performed by using a machine usually used for coarse pulverization of various materials such as a ball mill, a vibration mill, a cutter mill, a hammer mill, a wheelie mill, and a jet mill as its means.

  Hydrothermal treatment is a process in which the coarsely pulverized product obtained above is exposed to pressurized hot water in order to remove lignin from cellulose or hemicellulose. As for the conditions of the pressurized hot water in the hydrothermal treatment, the pressure is preferably 0.5 to 1.5 MPa, and the temperature is equal to or lower than the saturated vapor temperature at the pressure and preferably 140 to 200 ° C, particularly 160 to 180 ° C. Is preferred. The treatment time is preferably 30 to 120 minutes. By subjecting the coarsely pulverized product to hydrothermal treatment under the above conditions, a part of lignin is separated, and a part of hemicellulose is reduced in molecular weight by hydrolysis and becomes soluble. In general, the temperature of 140 to 200 ° C. is a temperature at which excessive decomposition hardly occurs during the conversion to monosaccharide. Specifically, the hydrothermal treatment can be performed in a pressure and heat resistant container whose temperature and pressure are adjusted so as to satisfy the above-mentioned preferable conditions by a normal heating and pressurizing means.

  Examples of the pretreatment means provided before the saccharification means further include means for fine pulverization treatment performed after the coarse pulverization treatment and hydrothermal treatment. In the pulverization treatment, the hydrothermally-treated product obtained above is pulverized to reduce the crystallinity and polymerization degree of cellulose and activate mechanochemically. (A) Easy enzymatic reaction in saccharification means It is a process that makes it easier to receive. This pulverization is preferably performed in a state where water remains. The fine pulverization treatment can be performed using, for example, a general fine pulverizer such as a vibration ball mill, a rotating ball mill, a planetary ball mill, a roll mill, a disk mill, a high-speed rotary blade mixer, and a homomixer as its means. The pulverization process is preferably performed until the average particle diameter of the processed product is on the order of several tens of micrometers.

(A) Saccharification means By the pretreatment by the pretreatment means, a slurry-like processed product (hereinafter referred to as “lignocellulose slurry”) is obtained from the woody lignocellulose raw material. (A) The saccharification means is means for converting (saccharifying) saccharification enzymes such as cellulase or hemicellulase to act on saccharification enzymes such as cellulase or hemicellulase to hydrolyze them. Here, conversion of lignocellulose into sugar (saccharification) in the present specification means conversion of polysaccharide contained in lignocellulose into sugar (saccharification).

  Cellulase is a general term for enzymes that hydrolyze cellulose. Specifically, exo-type cellobiohydrolase that releases cellobiose from the end of crystalline cellulose, which does not decompose crystalline cellulose, but randomly breaks amorphous cellulose chains Cellulases comprising a mixed enzyme containing three types of endo-type endoglucanases and exo-type β-glucosidases that generate glucose from the ends of cellobiose and short chains (cellooligosaccharides) are generally used.

The hemicellulase that hydrolyzes hemicellulose is a mixed enzyme such as, for example, endoxylanase, exoxylosidase, acetyl-xylanesterase, ferulic acid esterase, or the like, which degrades the binding of a plurality of sugars in hemicellulose.
These saccharifying enzymes vary in activity and mixing ratio of each enzyme depending on the source microorganism, and in the present invention, general enzymes commercially available as cellulase or hemicellulase can be used.

  (A) The saccharification reaction in the saccharification means can be carried out by the same method and conditions as those usually used when saccharifying the lignocellulose slurry using cellulase or hemicellulase. Since the saccharifying enzyme is a mixture of a plurality of enzymes as described above, it slightly differs depending on the saccharifying enzyme to be used. However, the lignocellulose slurry is diluted with a buffer solution so that the optimum pH range of the enzyme to be used is obtained. The saccharification reaction is carried out at an appropriate temperature range. According to a general saccharifying enzyme, the pH is about 3.5 to 5.5, the temperature is about 40 to 50 ° C., and the time is about 48 to 72 hours. This saccharification treatment may be performed batchwise or continuously using a bioreactor containing an immobilized enzyme.

  By performing saccharification treatment by the saccharification means (A), glucose derived from cellulose occupying most of the sugar, fructose derived from hemicellulose, hexose such as mannose, monosaccharide such as pentose such as xylose derived from hemicellulose, arabinose, or A sugar solution having an oligosaccharide capable of a small amount of ethanol fermentation and having a sugar concentration of several percent is obtained.

Next, (B) sugar concentration is performed by concentrating the sugar solution having a sugar content concentration of several percent obtained by the sugar concentration means. (B) Before the sugar concentration means, that is, after (A) the saccharification means, It is preferable to provide means for separating the lignocellulose residue that has not been saccharified by the saccharification means from the sugar solution. Here, the lignocellulose residue separated and removed from the sugar solution is used as an energy source by the method described later.
(A) The lignocellulose residue separated and removed from the sugar solution, which is the reaction solution after being subjected to the saccharification means, is a solid component mainly composed of lignin. General means for removal, such as filtration, can be applied without particular limitation. When performing separation by filtration, pressure filtration is used as a suitable means.

(B) Sugar solution concentrating means (B) The sugar solution concentrating means concentrates the sugar solution of several percent concentration obtained by the above (A) saccharification means to a suitable sugar concentration by the following (C) ethanol fermentation means. It is a means to do. The extent to which the sugar solution is concentrated depends on the yeast used for ethanol fermentation. In other words, the sugar solution is concentrated by this means in accordance with the sugar concentration in the optimum fermentation conditions of the yeast to be used. As a preferable sugar concentration of such a sugar solution, a sugar concentration of 10 to 22% by mass can be mentioned in accordance with the ethanol fermentation ability of yeast suitably used in the following (C) ethanol fermentation means. Further, from the same viewpoint, the more preferable concentration of the sugar solution is 14 to 17% by mass.

  As a specific means for concentrating the sugar solution, a means for concentrating the sugar solution generally used in the food industry can be used without any particular limitation. More specifically, each concentration means such as vacuum evaporation concentration, freeze concentration, membrane concentration and the like can be mentioned, and among these, membrane concentration is preferable from the viewpoint of suppressing energy consumption related to concentration. The type of membrane used for membrane concentration of the sugar solution is not particularly limited as long as the sugar solution can be concentrated under the above conditions, that is, a concentration of several percent to preferably a concentration of 22% by mass. Specific examples of such membrane concentration membranes include reverse osmosis membranes, ultrafiltration membranes, and nanofiltration membranes. In addition, as such a film, for example, a commercial product such as NTR-7250 manufactured by Nitto Denko Corporation can be used. When concentrating a sugar solution using a membrane, it is possible to perform operations by appropriately selecting appropriate conditions for each membrane.

(C) Ethanol fermentation means (C) The ethanol fermentation means uses yeast having ethanol fermentation ability to convert sugar in the sugar liquid concentrated by the sugar liquid concentration means to ethanol by ethanol fermentation. It is. As the yeast to be used, it is possible to use yeast that has been conventionally used for ethanol fermentation of sugars mainly composed of glucose without any particular limitation. In addition, there are many yeasts that have been genetically modified for various uses and added high functionality. From these, yeast having a function to enhance the effect of the present invention is selected, and this (C) ethanol It can also be used as a fermentation means, and is preferable. For example, if genetically modified yeast with pentose fermentation ability is used, not only cellulose-derived glucose but also hemicellulose-derived xylose and arabinose can be converted to ethanol, which can increase the efficiency of ethanol fermentation. It becomes.

  (C) About the conditions of ethanol fermentation in an ethanol fermentation means, it sets suitably according to the yeast to be used. Usually, using a fermenter, fermentation is carried out at a fermentation temperature of about 30 to 32 ° C. for about 48 to 96 hours.

(D) Ethanol separation and purification means (D) The ethanol separation and purification means separates and purifies ethanol from the ethanol fermentation solution obtained by the above (C) ethanol fermentation means, preferably to a purity of approximately 99.5% by mass or more. Means. Usually, the ethanol fermentation broth is mainly composed of water and ethanol, and contains other components such as unfermented sugar, acetic acid, furfural and the like as other minute components. As a specific means for separating and purifying ethanol from such ethanol fermentation broth, (D) ethanol separation and purification means is a conventionally known means, specifically, a distillation method or a distillation method and a membrane separation method or adsorption separation. Separation and purification means combined with a method can be used. Since a mixture of ethanol and water has an azeotropic point at an ethanol concentration of 95% by mass, it is necessary to perform azeotropic distillation in order to purify ethanol with a high purity by a distillation method. Is not preferable because it requires a lot of energy. In view of this, it is preferable to use a means in which the ethanol fermentation liquid is first purified to about 95 mass% by distillation and then purified to high purity ethanol by membrane separation and adsorption separation. The impurities contained in the ethanol fermentation liquid are separated and removed at the distillation stage.

  In the cellulose-based ethanol production system of the present invention, since the sugar solution is concentrated by the (B) sugar solution concentrating means, (C) the ethanol concentration in the ethanol fermentation solution obtained by ethanol fermentation by the ethanol fermentation means Therefore, the amount of energy required to separate and purify ethanol in (D) ethanol separation and purification means can be kept lower than that of the conventional method. In addition, the amount of energy required to perform the same level of concentration is higher than that of (D) concentration mainly in distillation in ethanol fermentation liquid of ethanol separation and purification means, and (B) concentration operation in concentration of sugar liquid in sugar liquid concentration means. Therefore, according to the present invention, it can be said that the energy consumption throughout the cellulosic ethanol production system is reduced. The difference in the amount of energy required to perform the same level of concentration between the ethanol fermentation liquor and the sugar liquor depends on the sugar molecular structure being larger than ethanol, but the energy consumed by the concentration operation of the sugar liquor concentration itself. The factor due to the small is greater.

  Moreover, since a part of the water in the sugar solution has been removed by the (B) sugar solution concentrating means, (C) the sugar solution to be treated by the ethanol fermentation means and (D) the ethanol separation and purification means. Both volumes of the ethanol fermentation liquor are reduced, and the capacity of the apparatus in (C) ethanol fermentation means and (D) ethanol separation and purification means can be kept small.

Here, the lignocellulose residue mainly composed of lignin separated from the sugar solution after the saccharification means (A) can be used as an energy source / fuel. As a preferred embodiment in which the lignocellulose residue is used as a fuel, as shown in FIG. 1, the lignocellulose residue obtained as described above is dried by a drying means as necessary, and a part or all of the fuel of the thermal power plant is obtained. The medium-low pressure superheated steam or exhaust gas generated by the thermal power plant is used as one of the means in the cellulose-based ethanol production system described above, specifically, ethanol separation / purification means or lignocellulose raw water. The aspect used as a heat source for heat processing, the drying means of a lignocellulose residue, etc. is mentioned.
Further, the distillation residue obtained during the separation and purification of ethanol can be dried as necessary by the ethanol separation and purification means (D) and used as a fuel in a thermal power plant.

  Thus, in the cellulosic ethanol production system of the present invention, the supply of fuel for power generation from the cellulosic ethanol production system to the installed thermal power plant, and the cellulosic ethanol production system for exhaust heat of the thermal power plant By using the above, it is possible to provide a cellulosic ethanol production system excellent in energy efficiency.

  Next, an embodiment of the cellulosic ethanol production system according to the present invention using the herbaceous lignocellulose raw material shown in FIG. 2 will be described. The herbaceous lignocellulose raw material to be used is not particularly limited as long as it is a herbaceous material. Specific examples include grasses, legumes, and biomass selected from these crop residues.

(Means related to pretreatment)
In the cellulosic ethanol production system according to the present invention, when a herbaceous lignocellulose raw material is used, (A) coarse pulverization treatment and water added as shown in FIG. It is preferable to provide means for performing each of the pulverization processes. Since lignocellulose contained in the herbaceous lignocellulose raw material has a lower lignin content than woody ones, it is easy to saccharify cellulose and hemicellulose without performing hydrothermal treatment as described above. The coarse pulverization process and the fine pulverization process with water added can be performed by the same means as the coarse pulverization process and the fine pulverization process in the case of using the above woody lignocellulose raw material.

  Subsequent (A) saccharification means, (B) sugar liquid concentration means, (C) ethanol fermentation means, and (D) ethanol separation and purification means are the same as in the case of using the above-mentioned woody lignocellulose raw material.

Here, also in the cellulosic ethanol production system using the herbaceous lignocellulose raw material, ligno that has not been saccharified from the sugar solution by the saccharification means before (B) the sugar concentration means, that is, after (A) the saccharification means. The cellulose residue is separated from the sugar solution by a suitable separation means, and / or (D) the distillation residue obtained during the separation and purification of ethanol by the ethanol separation and purification means is separated from the fermented ethanol by a suitable separation means. Can be used as fuel.
However, since herbaceous biomass generally contains a large amount of ash (inorganic matter), many ash content exceeds 10% when dried per se. Therefore, in ethanol production from herbaceous biomass, distillation obtained by distilling and separating from lignocellulose residue obtained by separation from sugar liquid after being subjected to saccharification means and ethanol fermentation liquid after being subjected to fermentation / distillation means The residue may contain as much as 30 to 40% ash, and when these residues are used as fuel, it is necessary to remove the ash from the residue.

  Therefore, in the embodiment in which the herbaceous lignocellulose raw material shown in FIG. 2 is used, after the separation means for separating the lignocellulose residue from the sugar solution, the separated lignocellulose residue is further converted into an inorganic substance (ash). A means for classifying into a component mainly composed of organic substances and a component mainly composed of organic substances is provided. The means used for classification of lignocellulose residue is not particularly limited as long as it can effectively separate the lignocellulose residue into inorganic-based components and organic-based components. Specifically, a centrifugal classifier is used. Can be done. The organic matter of the lignocellulose residue obtained here, mainly a component mainly composed of lignin, is used as the fuel. When the organic main component of the lignocellulose residue is used as a fuel, it is usually used after being dried by a drying means, but this drying may be performed before the above classification, or may be performed after the classification as shown in FIG. Good. When drying is performed before classification, a centrifugal classifier is used. When drying is performed after classification, a centrifugal classifier is used.

  In the lignocellulose residue, organic substances and inorganic substances exist with their own density distributions, and since they overlap each other, it is impossible to completely separate them using a separation method utilizing density differences. However, as shown in FIG. 3, classification to a certain extent is possible by utilizing the difference in density distribution between the organic substance and the inorganic substance. For example, it is possible to separate and remove the shaded portion of the inorganic substance by classification with the density of the broken line shown in FIG. The ratio of the inorganic substance to be separated and removed is determined according to the purpose of use of the treatment residue. However, as shown in FIG. 2, when the boiler fuel is used for thermal power generation, it is desirable to separate the ash to be about 8% or less. .

  In this way, it is possible to recover fuel suitable for power generation from lignocellulose residue after saccharification means for ethanol production using herbaceous biomass with high ash content as lignocellulose raw material. Although not shown in FIG. 2, the same treatment can be performed on the distillation residue after the fermentation / distillation means.

  As shown in FIG. 2, the organic substance main component of the lignocellulose residue obtained by the classification is dried by a drying means as necessary (the drying may be performed before classification in the state of lignocellulose residue). In addition, it can be used as a part or all of the fuel of the thermal power plant installed. Further, the medium- and low-pressure superheated steam or exhaust gas generated by this thermal power plant is converted into any one of the means in the cellulose-based ethanol production system described above, specifically, ethanol separation / purification means or the lignocellulose residue and its By using it as a heat source for drying means for organic components, the energy efficiency of this cellulose-based ethanol production system can be increased.

  Here, even in the conventional cellulose-based ethanol production system, that is, (B) the cellulose-based ethanol production system that does not have the sugar liquid concentration means, the lignocellulose after the saccharification means from the cellulose-based ethanol production system to the thermal power plant provided therewith The residue is dried as needed and supplied as a fuel for power generation, and the waste heat from the thermal power plant is used in the cellulosic ethanol production system, thereby providing a cellulosic ethanol production system with excellent energy efficiency. .

  Furthermore, even when (B) ethanol production using herbaceous biomass with a large amount of ash as a lignocellulose raw material is performed by a conventional cellulose-based ethanol production system that does not have a sugar liquid concentration means, B) Energy efficiency combining a thermal power plant and a cellulosic ethanol production system by recovering and using lignin-based organic matter suitable for power generation by removing ash from lignocellulose residue after saccharification means Production of cellulosic ethanol with good quality.

In addition, the method for producing cellulosic ethanol using the lignocellulose of the present invention as a raw material includes a saccharification step of converting lignocellulose into sugar using an enzyme, and a saccharide solution concentration step of concentrating the saccharide solution obtained by the saccharification step. And a fermentation step of fermenting the concentrated sugar solution with ethanol using yeast, and a step of separating and purifying ethanol from the ethanol fermentation solution obtained by the fermentation step.
Specifically, the saccharification step in the cellulose-based ethanol production method of the present invention can be performed by (A) saccharification means in the cellulose-based ethanol production system of the present invention. Similarly, the sugar liquid concentration step can be executed by the above (B) sugar liquid concentration means, the ethanol fermentation step by the above (C) ethanol fermentation means, and the ethanol separation and purification step by the above (D) ethanol separation and purification means. is there.
Thus, specifically, the ethanol production method of the present invention can be performed using the ethanol production system of the present invention, and is preferably executed by the ethanol production system of the present invention. It is not limited.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
Example 1
Example 1 will be described with reference to FIG. This example shows a cellulosic ethanol production system that is particularly suitable when using grasses or legumes such as rice straw as raw materials.

  Lignocellulosic biomass, which is a raw material for cellulosic ethanol production, is supplied from the raw material hopper 10 and coarsely pulverized by a coarse pulverizer 12 to a few millimeters in a dry manner. The coarse pulverizer 12 uses a shearing mill that enables the pulverization of plant fibers by rotating a large number of blades at high speed.

  The lignocellulose coarsely pulverized by the coarse pulverizer 12 is mixed with a high-temperature feed water preheated to about 80 to 90 ° C. and a stirring mixer 14 to be slurried (hereinafter referred to as lignocellulose slurry). Here, the amount of water supply is about 6 to 8 times by weight with respect to the dry weight of the supplied lignocellulose. The appropriate amount of water supply varies depending on the cellulose raw material, but is determined mainly in consideration of the efficiency of pulverization in the fine pulverizer 19.

  Next, the lignocellulose slurry is sent to the fine pulverizer 19 by the supply pump 15, and is pulverized wet by the fine pulverizer 19 to the order of several tens of micrometers. A mortar-type mill that applies a strong shearing force to the object to be crushed is suitable for the pulverizer 19.

  The finely pulverized lignocellulose slurry is sent to the enzyme reaction tank 22. In the enzyme reaction tank 22, cellulase or a mixed enzyme of cellulase and hemicellulase is charged, and undegraded cellulose or hemicellulose is subjected to an enzymatic saccharification reaction at about 40 to 50 ° C. while stirring the inside of the enzyme reaction tank 22. As a result, a mixed slurry of a sugar solution having a sugar concentration of several percent containing hexose such as glucose and pentose such as xylose and an unreacted saccharification residue (lignocellulose residue) is obtained.

  The mixed slurry subjected to the enzymatic saccharification treatment is solidified into a saccharification residue (solid component) mainly containing organic matter such as lignin and ash (inorganic matter) and a sugar solution (liquid component) such as glucose and xylose by the residue separator 25. Separate the liquid. The residue separator 25 is a filter press type separator, and the mixed slurry is supplied by being pressurized by a pressure pump 24. In the case where cake filterability is low due to the properties of the residual components, it is also effective to apply a belt press type separator.

  The sugar liquid separated by the residue separator 25 is sent to the sugar liquid concentration membrane 32 without reducing the pressure, and a part of water is dehydrated by membrane separation at the sugar liquid concentration membrane 32, and the concentration of the sugar liquid is preferably 10 to 22 weights. %, More preferably, it is concentrated so as to be 14 to 17% by weight.

  Next, ethanol fermentation of the sugar solution is performed in the yeast fermenter 34 by the action of the yeast. The yeast fermenter 34 is cooled as necessary to maintain an appropriate temperature of the yeast to be used. In recent years, special yeast capable of ethanol fermentation of pentose has been developed, and ethanol fermentation of pentose such as xylose in a sugar solution is also possible by using such yeast.

  The fermented ethanol is sent to the mash distillation column 42 and the concentration distillation column 44 and concentrated by distillation. Here, in addition to dehydration, impurities such as unfermented sugar and furfural contained in the fermented ethanol are separated and removed. Through the moromi distillation tower 42 and the concentration distillation tower 44, the fermented ethanol is concentrated to 90 to 94% by weight. Further, 99.5% by weight or more of absolute ethanol is purified by dehydration in the vapor permeable separation membrane in the dehydration membrane 46.

  On the other hand, the saccharification residue separated by the residue separator 25 is sent to the centrifugal classifier 52. In the centrifugal classifier 52, organic substances such as lignin contained in the saccharification residue and ash (inorganic content) are separated by a wet process.

  Next, the organic matter containing lignin is dried by the residue drier 54 to obtain a dried product of the saccharification residue that can be used as a fuel for power generation.

  Further, as shown in FIG. 2, the cellulosic ethanol production system supplies the power generation fuel from the residue dryer 54 as the fuel for the thermal power plant provided therewith. Low-pressure superheated steam at 150 ° C. or lower from a thermal power plant is supplied to the mash distillation column 42 and the concentrated distillation column 44 and used as a heating source for distillation. In addition, the exhaust heat of the thermal power plant is supplied to the residue dryer 54 and effectively used as a heat source for residue drying.

(Example 2)
Next, Example 2 will be described with reference to FIG. This example shows a cellulosic ethanol production system suitable particularly when woody lignocellulose having a low ash content and a high lignin content is used as a raw material. In addition, the same code | symbol is attached | subjected to the structure same as Example 1, and the overlapping description is abbreviate | omitted.

  The coarse pulverizer 12 uses an impact mill that pulverizes with impact or shear force by rotating a hammer or blade at high speed. By this, it is coarsely pulverized by a dry method to a particle size of about several mm.

  The obtained lignocellulose slurry is pressurized to 0.5 to 1.5 MPa by the pressure supply pump 16 and sent to the hydrothermal reactor 17. By heating with superheated steam from the surroundings in the hydrothermal reactor 17, the cellulose slurry is heated to about 140 to 200 ° C. which is lower than the saturated steam temperature of pressurized water near the outlet of the hydrothermal reactor 17. In particular, 160 to 180 ° C. is appropriate. The water slurry inside the hydrothermal reactor 17 is in the state of pressurized hot water.

  The saccharification residue (lignocellulose residue) separated by the residue separator 25 is directly dried by the residue dryer 54 to obtain a dried product of the saccharification residue that can be used as a power generation fuel.

  Furthermore, as shown in FIG. 1, the cellulosic ethanol production system uses a low-medium pressure superheated steam of 200 ° C. or less of a thermal power plant provided as a heating source of the hydrothermal reactor 17.

  The cellulosic ethanol production system of the present invention can be effectively used as a cellulosic ethanol production system that efficiently produces ethanol from lignocellulose as a raw material.

10: raw material hopper 12: coarse pulverizer 13: water supply valve 14: stirring mixer 15: supply pump 16: pressure supply pump 17: hydrothermal reactor 18: pressure regulating valve 19: fine pulverizer 22: enzyme reaction tank 24 : Pressure pump 25: residue separator 32: sugar liquid concentration membrane 32: yeast fermentation tank 42: moromi distillation column 44: concentration distillation column 46: dehydration membrane 52: centrifugal classifier 54: residue dryer

Claims (10)

A cellulosic ethanol production system for producing ethanol from lignocellulose,
A saccharification means for converting lignocellulose into sugar using an enzyme, a sugar liquid concentration means for concentrating the sugar liquid obtained by the saccharification means, and a fermentation means for subjecting the concentrated sugar liquid to ethanol fermentation using yeast. And a means for separating and purifying ethanol from the ethanol fermentation broth obtained by the fermentation means.   2. The cellulose-based ethanol production system according to claim 1, wherein the concentration in the sugar liquid concentrating means is concentration in which the sugar concentration of the sugar liquid is 10 to 22% by weight.   The cellulosic ethanol production system according to claim 1 or 2, wherein the concentration in the sugar liquid concentration means is membrane concentration.   The cellulosic ethanol production system according to any one of claims 1 to 3, further comprising means for separating lignocellulose residue that has not been saccharified by the saccharification means from the sugar solution after the saccharification means.   The cellulosic system according to claim 4, further comprising means for classifying the separated lignocellulose residue into a component mainly composed of an inorganic substance (ash) and a component mainly composed of an organic substance, following the means for separating the lignocellulose residue. Ethanol production system.   The cellulose-based ethanol production system according to claim 5, wherein a wet or dry centrifugal classifier is used as a means for classifying the lignocellulose residue.   The cellulosic ethanol production system according to claim 5 or 6, wherein the lignocellulose is a lignocellulose derived from a biomass selected from a gramineous plant, a leguminous plant, and a crop residue thereof.   The separated lignocellulose residue or the classified lignocellulose residue is used as a part or all of the fuel of the thermal power plant provided with the organic component, and the medium-low pressure superheated steam generated by the thermal power plant or The cellulosic ethanol production system according to any one of claims 4 to 7, wherein the exhaust gas is used for any of the means in the ethanol production system.   The method further comprises means for drying the separated lignocellulose residue or the organic component of the classified lignocellulose residue, and the medium-low pressure superheated steam or exhaust gas generated by the thermal power plant is separated and purified by ethanol. 9. The cellulosic ethanol production system according to claim 8, wherein the system is used for the drying means. A method for producing cellulosic ethanol that produces ethanol using lignocellulose as a raw material,
A saccharification step for converting lignocellulose to sugar using an enzyme, a saccharide solution concentration step for concentrating the saccharide solution obtained by the saccharification step, and a fermentation step for ethanol fermentation of the concentrated saccharide solution using yeast. And a step of separating and purifying ethanol from the ethanol fermentation liquid obtained by the fermentation step.

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