JP5165419B2 - Bioethanol production system using lignocellulose as a raw material - Google Patents

Description

  The present invention relates to a system and method for producing bioethanol from lignocellulose as a raw material. The present invention relates to a bioethanol production system that makes maximum use of recovered heat energy and the like in a pulp factory equipped with a facility for co-producing pulp by a kraft method and a sulfite method and a bioethanol production facility.

  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, and is a technology that produces lignocellulose as a biomass raw material and produces ethanol by ethanol fermentation. Interest is extremely high.

Bioethanol using lignocellulose as a raw material Generally, 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 microorganisms. It is performed by converting into ethanol by the action of yeast or the like. The methods for degrading polysaccharides such as cellulose and hemicellulose into sugars are (1) acid saccharification method using a mineral acid and (2) enzyme saccharification method using an enzyme or a microorganism that produces the enzyme. Broadly divided. 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 concentrated sulfuric acid method, the hydrolysis of lignocellulose proceeds relatively easily, and the glucose derived from the obtained sugar is subjected to ethanol fermentation. However, when the concentrated sulfuric acid method is applied industrially, it is necessary to separate concentrated sulfuric acid and glucose, and collect and reuse concentrated sulfuric acid. Also, at first glance, the production cost seems to be low, but because the corrosion of the equipment due to sulfuric acid is severe, the use of special materials and equipment that can withstand sulfuric acid corrosion is unavoidable, and the capital investment is enormous. In addition to this, the labor and cost required for maintenance and management of facilities are extremely high, and there is a great danger in operation. Furthermore, in order to obtain a sugar with a high yield, pretreatment such as making lignocellulose into a powder form or sufficiently drying is necessary, so that further power and thermal energy costs are required. Furthermore, it is necessary to treat the residual lignin, but it is very difficult to handle because lignin is insoluble in water. For example, when lignin is used as a fuel, since lignin is insoluble in water, it is not possible to apply a process of spraying and burning in a recovery boiler used in a pulp production facility described later. For this reason, methods for separating, recovering, washing, neutralizing, drying, pelletizing and burning residual lignin have been proposed. Cost and hassle. Moreover, since a twin screw extruder etc. are needed for pelletization, in order to utilize biomass comprehensively, a manufacturing process will become complicated. Although there is a possibility that lignin can be used for other purposes, no specific application field has been found.

  The dilute sulfuric acid method also has the same problems as the concentrated sulfuric acid method. Furthermore, in the case of the dilute sulfuric acid method, the hydrolysis requires a plurality of steps. Moreover, the dilute sulfuric acid used for the hydrolysis is not recovered and reused, and needs to be neutralized after use and treated as gypsum. Further, it is difficult to say that the saccharification rate is at a sufficient level, and only hemicellulose and relatively low molecular weight cellulose are decomposed. As a method for improving the saccharification rate, strengthening of treatment conditions and combined use of concentrated sulfuric acid have been studied. However, when excessive treatment is performed, a problem such as degeneration of sugar into a fermentation inhibitor or the like newly arises.

  In order to solve these problems, a method in which the process is simplified (Patent Document 1), a method using concentrated sulfuric acid (Patent Document 2), a sulfuric acid method, and a technique for solving the problems of the dilute sulfuric acid method are applied with pressure Although a method using water (Patent Document 3) has been proposed, it is difficult to say that all of the conventional problems have been sufficiently solved, and there has been no study on effective use of lignin remaining as a residue. Absent.

  On the other hand, in the enzymatic saccharification method, the lignocellulose as a raw material is generally pretreated and subjected to an enzyme treatment. Examples of the pretreatment include prehydrolysis with dilute acid and high-temperature water, alkali treatment, and the like, and this is mainly carried out to remove lignin components that inhibit the enzyme reaction. The pretreatment waste liquid contains lignin, hemicellulose, etc., but is discarded without being effectively used. Following the pretreatment, lignocellulose is saccharified by the action of degrading enzymes, but it is difficult to say that saccharification efficiency is high due to inhibiting factors such as residual lignin. For this reason, since it is necessary to use a large amount of expensive enzymes, a cost increase cannot be avoided, and there is a problem that profitability does not match when industrialized. As a solution to these problems, a method of recovering the enzyme used for saccharification by ultrafiltration or the like has been considered, but the present situation is that the enzyme is not sufficiently recovered by adsorbing to lignocellulose residue or the like. . Moreover, although the method (patent document 4) which suppresses the loss of an enzyme by providing a continuous saccharification tank is proposed, it has problems, such as requiring a long time for a process. Moreover, although the method (patent documents 5, 6) and the method of hydrothermal processing (patent documents 7, 8) which are acid-treated as a pre-process of enzyme treatment are proposed, neither has reached the solution of a subject.

  As described above, the production of bioethanol from lignocellulose by the acid saccharification method or the enzymatic saccharification method is not only very inefficient and expensive, but also an effective system from the viewpoint of effective use of biomass. hard. In addition, the conventional technology is only being implemented and studied in a test plant and a small-scale test manufacturing facility, and an effective system capable of mass production commercially has not yet been established. Therefore, 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 corn that is easily decomposed into monosaccharides, It is currently manufactured from cereal raw materials such as wheat and molasses.

Pulp manufacturing process As a large-scale facility for handling lignocellulose, there is a pulp manufacturing facility. In general, a wood pulp manufacturing process has been established on a commercial scale and is known to be a very efficient system.

  As a method for producing bioethanol using lignocellulose as a raw material, a method using pulp black liquor (particularly, black liquor by sulfite method) by-produced in a wood pulp production process is known. Black liquor is a solution produced as a by-product by cooking wood chips under high temperature and high pressure using a chemical solution, and contains elution components from wood other than the chemical solution and fiber.

Kraft (KP) Method The pulp production method is roughly divided into a kraft (KP) method and a sulfite (SP) method. The kraft method is excellent in terms of pulp yield and pulp strength, and is characterized by solubilizing and removing lignin in wood chips. Because of its excellent pulp yield and pulp strength, many papermaking pulps are currently produced by the kraft method.

  Dissolve caustic soda and sodium sulfide in water to prepare a cooking solution, solubilize and remove lignin under alkaline conditions to take out cellulose fibers (kraft pulp) containing a high amount of hemicellulose. Kraft black liquor contains organic components such as lignin and inorganic components such as cooking chemicals, but does not contain much monosaccharide components that can be used for ethanol fermentation. For this reason, kraft black liquor is usually concentrated and then sprayed and burned into a recovery boiler in the form of a mist. Organic substances such as lignin are generally recovered and reused as thermal energy and inorganic substances as cooking chemicals. . At that time, sodium sulfate is added to replenish sodium and sulfur lost in a series of processes. Inorganic substances are mainly recovered as sodium carbonate and sodium sulfide, but these inorganic substances are taken out from the bottom of the recovery boiler in a molten state called smelt. The smelt taken out from the recovery boiler is dissolved in water or a weak liquid (a liquid containing a small amount of white liquor component obtained after washing calcium carbonate with water) to become a green liquid. Furthermore, sodium carbonate in the green liquor is converted to sodium hydroxide, which is a cooking chemical, by a subsequent causticizing step. The causticizing process consists of (1) a soothing reaction that converts quick lime to slaked lime, and (2) a causticizing reaction that mixes slaked lime and green liquor to produce sodium hydroxide and light calcium carbonate. The resulting liquid is called white liquor, separated and clarified from light calcium carbonate, and sent to the cooking process.

  However, the problem of the recovery process in the kraft method is that the recovery rate balance of sodium and sulfur varies and it becomes difficult to keep the balance of the entire system optimal. For example, when the degree of sulfidation becomes too high, it is necessary to release sulfur from the system. Further, in a factory where the alkali recovery rate is extremely high and the amount of sodium sulfate replenished is small, it is necessary to adjust the amount of sodium recovered, or the addition or replenishment of sulfur.

  Moreover, as a method for increasing the cellulose content in pulp by the kraft method, there is a prehydrolysis kraft (PHKP) method in which hydrolysis is performed as a pretreatment for cooking. In the PHKP method, pre-hydrolysis is performed as a pretreatment for kraft cooking, and in the pre-hydrolysis process, wood chips are generally treated under conditions of 170 to 240 ° C, and the bond between hemicellulose and cellulose is broken by the action of water or dilute acid. To do. The black liquor generated by the prehydrolysis contains hemicelluloses such as xylan and glucomannan separated from cellulose, and monosaccharides produced by the decomposition of these hemicelluloses. However, since the amount of monosaccharide is not sufficient, in order to use the black liquor generated in the prehydrolysis for ethanol fermentation, a treatment such as rehydrolysis of hemicellulose in the black liquor is required (Patent Document 9). ). Moreover, since the produced | generated saccharide | sugar changes into ethanol fermentation inhibitors, such as a furfural and a tar, when a prehydrolysis process is excessive, optimization of a process condition becomes essential (nonpatent literature 1). In addition, lignin in wood is also separated to some extent by prehydrolysis, but these lignins are insoluble in water and may cause mechanical troubles by condensation and precipitation due to the action of acids. In addition, the recondensed lignin is easily re-adsorbed on the fiber surface, and the subsequent kraft cooking hardly promotes delignification. Since these problems are particularly prominent in coniferous trees, the prehydrolysis method is rarely applied to coniferous wood, and the tree species that can be used are also limited. For the above reasons, kraft black liquor generated by prehydrolysis is rarely used for ethanol fermentation.

Sulphite (SP) method The sulphite method is superior in that a pulp having a high cellulose content can be produced, and is characterized by solubilizing and removing lignin in wood. In many cases, wood chips are digested under acidic conditions using chemicals that have absorbed sulfur dioxide. Lignin is changed to lignin sulfonic acid to solubilize, and hemicellulose is removed by hydrolysis to take out cellulose fibers (sulfite pulp). The cooking base includes calcium base, magnesium base, ammonia base, sodium base and the like. In the calcium-based sulfite method, it is difficult to digest tree species that contain a high amount of phenolic components and tannins, so the number of trees that can be used is limited, but it can be used with the advancement of technology using soluble bases. The number of tree species has increased. In particular, the base based on sodium has a wide range of applications, and bamboo, which has been considered difficult to use in the conventional sulfite method, can be used.

  The black liquor produced as a by-product of the sulfite method is rich in lignin sulfonic acid, inorganic components such as cooking chemicals, and sugars produced by hydrolysis of hemicellulose and cellulose, making it a useful woody biomass resource. It is used as. For example, lignin sulfonic acid in black liquor is water-soluble in the acidic to neutral range, easy to handle, and excellent in caking and dispersibility, so it is a concrete admixture, dye dispersant, coagulant, and dust as a liquid or powder product. Used in applications such as anti-scattering agents.

  In addition, as described above, the black liquor is rich in sugars, so nutrient sources such as ammonia, ammonium phosphate, and urea are added to serve as nutrient sources for feed yeast culture and ethanol fermentation. It has been. In general, Tolula yeast or the like has been used for culturing feed yeast, and Saccharomyces yeast has been used for ethanol fermentation. However, since Saccharomyces yeast consumes only hexose in black liquor, ethanol fermentation using sulfite black liquor requires coniferous sulfite black liquor rich in hexoses such as glucose, mannose and arabinose as sugar components. Is mainly used, and hardwood sulfite black liquor containing a large amount of pentose such as xylose has been regarded as inappropriate due to poor ethanol production efficiency. In this way, ethanol fermentation using sulfite black liquor can only be carried out in pulp mills that sulfite digest conifers, so it has been steadily decreasing and currently there are very few factories that are commercialized. is there. However, in recent years, genetically modified bacteria that produce ethanol using pentose have been invented, and further effective utilization of sulfite black liquor is expected regardless of conifers and broadleaf trees.

  Further, a method of recovering sulfite black liquor as thermal energy and inorganic chemicals by burning it with a recovery boiler has been conventionally performed in the same manner as kraft black liquor. However, the sulfite method has a problem that different chemical recovery steps are required depending on the base used for cooking. When using a magnesium base, the magnesium content is recovered through magnesium oxide, and the sulfur content is recovered via sulfurous acid gas and reused as cooking chemicals. On the other hand, when using a sodium base, the sodium content in the sulfite black liquor is recovered as sodium carbonate and the sulfur content as sodium sulfide in the same process as kraft black liquor. Since it cannot be used by the method, it is necessary to convert it into a usable chemical through a further process, and it is a big problem that a plurality of processes are required for collecting the chemical. Since different chemical recovery steps are required depending on the base, it is not easy to change the base in the sulfite equipment. For example, when the base is changed to sodium in a manufacturing facility that conducts magnesium-based sulfite cooking, the recovery boiler for magnesium cooking currently used cannot be diverted. A new recovery boiler is required, and a large capital investment is inevitable.

Combined use of KP method and SP method As a method to solve the problems in the chemical recovery process of the sulfite method as described above, during the technology transition period of papermaking raw material pulp (time to switch from SP method to KP method), SP It was proposed that KP equipment be installed side by side with sodium carbonate and sodium sulfide recovered from sulfite black liquor as supplementary chemicals for kraft cooking (so-called cross recovery method). However, it did not reach widespread use at the commercial level, and only the recovery of sulfite black liquor as thermal energy by combustion was studied. Thus, in the conventional cross recovery method, components such as lignin sulfonic acid and sugar contained in sulfite black liquor have not been effectively used.
Japanese Patent Laid-Open No. 2005-229821 JP-A-2005-229822 Japanese Patent Laid-Open No. 2007-20555 Japanese Patent Laid-Open No. 2006-87319 Japanese Patent Laid-Open No. 2006-24671 Japanese Patent Laid-Open No. 2007-104983 Japanese Patent Application Laid-Open No. 2007-74992 Japanese Patent Laid-Open No. 2006-141244 US Pat. No. 5,424,417 Wood and Fiber Science, April, 1986, Vol.18 (2) P248-263

  An object of the present invention is to provide an efficient system using an ethanol fermentation method, a kraft method, and a sulfite method.

  As a result of diligent studies, the inventors of the present invention have developed an extremely efficient lignocellulose utilization system in which the three parties are combined organically and work together by using the ethanol fermentation method, the kraft method, and the sulfite method together. It was found that it can be constructed, and the present invention was completed.

  The present invention can be evaluated from various viewpoints from various viewpoints. If attention is paid to products obtained from the system of the present invention, a system (apparatus) and method for producing bioethanol, and kraft pulp are produced. System and method, system and method for producing sulfite pulp, system and method for producing lignin sulfonic acid, system and method for producing calcium carbonate, system and method for recovering thermal energy Can be evaluated.

  From one aspect, the present invention is a system (apparatus) for effectively utilizing lignocellulose, and a kraft cooking apparatus for kraft cooking a first lignocellulose raw material to obtain kraft pulp and kraft black liquor; A sulfite cooking apparatus for sulfite cooking the second lignocellulose raw material on a sodium basis to obtain sulfite pulp and sulfite black liquor; an ethanol fermentation apparatus for ethanol fermentation of the sulfite black liquor to obtain ethanol and a fermented liquor And a cooking chemical recovery device for recovering the cooking chemical contained in the kraft black liquor and the fermented liquid and sending the recovered cooking chemical to the kraft cooking device.

  From another viewpoint, the present invention is a process (method) for effectively utilizing lignocellulose, wherein the first lignocellulose raw material is kraft-digested to obtain kraft pulp and kraft black liquor; A step of sulfite digesting the lignocellulose raw material of 2 with sodium base to obtain sulfite pulp and sulfite black liquor; a step of ethanol fermentation of the sulfite black liquor to obtain ethanol and a fermented liquor; Recovering the cooking chemical from the kraft black liquor and sending the recovered cooking chemical to the kraft cooking process.

  In the present invention, the lignocellulose raw material is a raw material containing lignin and cellulose, and is mainly composed of lignin, hemicellulose, and cellulose. In the present invention, ethanol, pulp, lignin sulfonic acid, energy, and the like can be obtained using lignocellulose as a raw material.

  Examples of the lignocellulose raw material include wood such as hardwoods and conifers, and agricultural residues such as straw and corn residues. There is no restriction | limiting in particular in the form of a raw material, For example, it can be used with a shape as it is, and what was processed into chip shape, powder shape, plate shape, etc. can also be used. The chip shape is preferable because of easy handling and high utilization efficiency. Moreover, it is also possible to use a material prepared from forest land remnants, bamboo, thinned wood, construction waste, etc. as a lignocellulose raw material. In the present invention, one kind of lignocellulose raw material can be used, and a plurality of lignocellulose raw materials can be used in combination.

  In the present invention, the lignocellulose raw material is used in both kraft cooking and sulfite cooking. The lignocellulose raw material used in kraft cooking and the lignocellulose raw material used in sulfite cooking may be the same or different and can be selected according to the business purpose. Since the sulfite cooking of the present invention is based on sodium, it can be cooked in a wide pH range, and as a result, there are almost no restrictions on tree species. Therefore, in the sulfite digester of the present invention, lignocellulosic raw materials such as forest land remnants, bamboo, thinned wood, and building waste can be suitably treated.

  The system of the present invention includes a kraft cooking apparatus for kraft cooking lignocellulose raw materials. Here, the kraft cooking means cooking by the kraft method, and the kraft method means cooking wood and other lignocellulose raw materials with a chemical solution mainly composed of sodium hydroxide and sodium sulfide. In this invention, a kraft pulp and a kraft black liquor are obtained by processing a lignocellulose raw material with a kraft cooking apparatus. The cooking method may be a batch type or a continuous type, but is preferably a continuous type. There is no particular limitation on the cooking conditions, and the kraft cooking apparatus can be operated under the conditions normally used. As the cooking equipment, equipment called a digester is usually used. The type of digester is not particularly limited, but for example, a Kamiya digester can be preferably used.

  The system of the present invention includes a sulfite cooking apparatus for sulfite cooking a lignocellulose raw material. In the present invention, sulfite cooking means cooking by the sulfite method, and the sulfite method is also called a sulfite method, which means cooking lignocellulose raw material using sulfurous acid. In the present invention, by treating the lignocellulose raw material with a sulfite digester, the lignin is sulfonated and dissolved to obtain sulfite pulp and sulfite black liquor.

  In general, the sulfite method can be classified into an acidic sulfite method, a bisulfite method, and a method using a sulfite, and a modified method based on these methods, a two-stage cooking method, and the like are known. In the present invention, these sulfite methods can be applied. The cooking method may be a batch type or a continuous type, but is preferably a continuous type. Although there is no restriction | limiting in particular about cooking conditions, For example, it can carry out at the temperature of 100 to 300 degreeC, the pressure of 2 to 10 atmospheres, etc.

  In the present invention, sodium base is used as the base of the cooking liquor. In general, as a base in the sulfite method, a soluble base such as magnesium, sodium, and ammonium, a calcium base, and the like are known. In the present invention, a sodium base is used. In the present invention, the cooking chemical contained in the sulfite black liquor is recovered by a recovery device to be described later and reused as the kraft cooking chemical in the kraft cooking equipment. Recycling of chemicals is easy and no special equipment is required. Sodium-based cooking is also preferable in that it has a wider applicable pH range than other bases and there are few restrictions on the tree species that can be used.

  The system of the present invention includes an ethanol fermentation apparatus for ethanol fermentation of sulfite black liquor to obtain ethanol and a fermented liquid. The sulfite black liquor obtained by the sulfite cooking equipment includes cooking chemicals, lignin sulfonic acid, hemicellulose and sugar produced by hydrolysis of cellulose. In the present invention, the cooking chemical in the sulfite black liquor is recovered and recycled in the recovery step described later, but the sugar in the sulfite black liquor is ethanol fermented in an ethanol fermentation apparatus. Ethanol obtained as a result of ethanol fermentation is so-called bioethanol produced from biomass resources. In ethanol fermentation, sugar in black liquor is converted to ethanol by the activity of microorganisms and yeast. As yeast used in the present invention, in addition to S. cereviseae conventionally used for ethanol fermentation of sulfite black liquor, strains and C. A yeast having ethanol fermentation ability such as krusei can be mentioned. Examples of microorganisms include E.coli strains that have ethanol fermentation ability through genetic engineering, Z.mobilis, strains that have been genetically engineered to have pentose utilization ability, C. glutamicum, and mutants thereof. Although it can be disclosed, any bacteria can be used as long as it is capable of ethanol fermentation, and one suitable for the composition of black liquor, fermentation conditions, and the like may be selected. In ethanol fermentation, it is also preferable to add a nutrient source such as ammonia, ammonia phosphate, or urea.

  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.

  In a preferred embodiment of the present invention, lignin sulfonic acid in sulfite black liquor can be removed. Lignin sulfonic acid is soluble in water from acidic to neutral, easy to handle, and excellent in caking and dispersibility, so it can be used as a liquid or powder product for concrete admixture, AE water reducing agent for cement, vanillin bottoming material, dye dispersion It can be used in applications such as agents, coagulants, and dust scattering inhibitors.

  In a preferred embodiment of the present invention, lignin sulfonic acid can be removed from the fermented liquid after ethanol fermentation of the sulfite black liquor. The main component of the fermented liquor is lignin sulfonic acid, but the lignin sulfonic acid in the fermented liquor can be taken out and commercialized and shipped, and the lignin sulfonic acid in the fermented liquor can be recovered by thermal energy using a recovery boiler It can also be used as Whether the lignin sulfonic acid contained in the fermented liquor is to be used as thermal energy or shipped as a lignin sulfonic acid product may be changed as appropriate in consideration of the operating status of the system and the effects and added value that are produced. Determine the ratio within the range that does not break the good balance of the system.

  The present invention further includes a cooking chemical recovery apparatus that recovers cooking chemicals contained in the kraft black liquor and the fermented liquid, and sends the recovered cooking chemicals to the kraft cooking apparatus. As a cooking chemical recovery apparatus, those commonly used in the technical field (filtration, centrifugation, etc.) can be used, but it is preferable to include a recovery boiler. In the present invention, cooking chemicals used for kraft cooking are recovered from kraft black liquor from kraft cooking and fermented liquid from sulfite cooking and recycled. Here, the cooking chemical contained in the kraft black liquor and the cooking chemical contained in the fermented liquor obtained by ethanol fermentation of the sulfite black liquor differ in the composition of sodium and sulfur, so the kraft black liquor and the fermented liquor By adjusting the balance, it becomes easy to keep the balance of the kraft cooking system optimal. That is, in a closed system including a recovery cycle, it has a problem that it is difficult to keep the mass balance in the system optimal. However, in the present invention, two compositions having different compositions of kraft black liquor and fermented liquor are used. In order to recover the cooking chemical from the source, it is easy to keep the balance of the system optimal by adjusting the ratio of both appropriately.

  In order to facilitate the optimization of such a system, the present invention may include a controller that adjusts the balance between the kraft black liquor and the fermented liquor to the cooking chemical recovery apparatus. The control method is not particularly limited, but so-called feedback control, control of the flow rate by setting a predetermined concentration and quantity, and the like are possible.

  When the cooking chemical recovery apparatus comprises a recovery boiler, the organic content contained in the kraft black liquor and the fermented liquid is combusted by the recovery boiler and used as thermal energy in the system. The recovered thermal energy can be used in any process. For example, the recovered thermal energy can be used for the most energy-intensive distillation / purification process in the bioethanol manufacturing process. Can be reduced. On the other hand, cooking chemicals (sodium content and sulfur content) contained in the kraft black liquor and the fermented liquor are recovered as smelt from the recovery boiler and reused in the kraft cooking equipment.

  The cooking chemical recovery apparatus of the present invention may further include a concentrating device for concentrating the black liquor or the fermented liquid before the recovery boiler or the like. The black liquor and the fermented liquor can be efficiently treated with a recovery boiler or the like by the treatment by the concentrator. As the concentrator used in the present invention, a general apparatus can be used. From the viewpoint of thermal efficiency, a multi-effect evaporator is preferable.

  The cooking chemical recovery apparatus of the present invention can perform a causticizing step of causticizing white liquor obtained from a recovery boiler or the like. In the causticizing step, calcium carbonate and sodium hydroxide can be obtained from the white liquor, which is preferable. Calcium carbonate can be used as a white powder for various applications. For example, calcium carbonate can be used as a papermaking material as a filler or filler, or can be sold as a commercial product. On the other hand, sodium hydroxide can be used as a cooking chemical in a kraft cooking apparatus.

The cooking chemical recovery apparatus of the present invention can further include a separation device for separating calcium carbonate and sodium hydroxide obtained from the causticizing step.
The system of the present invention may include a saccharification device that saccharifies sulfite pulp obtained in the sulfite cooking step. According to the saccharification equipment, not only the sulfite black liquor obtained by the sulfite digester but also sulfite pulp can be used for ethanol fermentation, and it is possible to produce a lot of bioethanol from lignocellulose raw material become.

  As the enzyme used in the present invention, any cellulase capable of degrading cellulose to glucose can be used. However, it has thermostability and has a balanced degradation activity of endo-glucanase / exo-glucanase / β-glucosidase. Higher one is desirable. For example, a mixture of cellulases NS50013 and NS50010 manufactured by Novo, Optimash BG manufactured by Genencor Kyowa, Sumiteam AC manufactured by Shin Nippon Chemical Industry Co., Ltd., and the like can be preferably used, but are not limited thereto.

According to the present invention, for example, the following effects can be obtained.
(1) Bioethanol can be produced by making the most effective use of the characteristics of sulfite black liquor and the thermal energy recovered by this system.
(2) Comprehensive effective use of biomass is possible, and social contribution is high.
(3) New business development and diversification will be possible by using existing kraft cooking equipment scattered in Japan and overseas and only installing sulfite cooking equipment.
(4) Since the lignocellulose collection route established in pulp production can be used, it is easy to procure various lignocellulose raw materials.
(5) Since the ethanol-fermented liquid can be burned using the recovery boiler of the KP manufacturing facility, it is not necessary to newly install a recovery boiler for sulfite black liquor. In addition, the complicated chemical recovery process required for conventional sodium-based sulfite cooking is not required.
(6) By mixing ethanol fermented liquor and kraft black liquor in an arbitrary ratio and combusting with a recovery boiler, it becomes easy to maintain the optimum balance of sodium and sulfur in kraft white liquor.

Hereinafter, the present invention will be described with specific preferred embodiments.
FIG. 1 is a schematic view showing a preferred embodiment of the system of the present invention, in which only sulfite black liquor is used for ethanol fermentation. The present invention in this aspect comprises a kraft cooking apparatus for kraft cooking a first lignocellulose raw material to obtain kraft pulp and kraft black liquor; a second lignocellulosic raw material sulfite digesting on a sodium basis; A sulfite digester for obtaining sulfite black liquor; an ethanol fermentation apparatus for ethanol fermentation of sulfite black liquor to obtain ethanol and a fermented liquor; and recovering and collecting the cooking chemicals contained in kraft black liquor and fermented liquor And a cooking chemical recovery device for feeding the cooking chemical to the kraft cooking device.

  In this embodiment, the lignocellulose raw material is digested with a sodium-based sulfite digester to obtain sulfite black liquor and sulfite pulp in the digester. Also, the sulfite cooking of the present invention must be a sodium based cooking process. By using sodium as the base, the sulfite black liquor and the ethanol-fermented liquid can be used for the recovery process of the KP facility. As a result, the present invention eliminates the need for a complicated chemical recovery installation process that is carried out in the conventional sodium-based sulfite cooking, so that the present invention can be reduced from the viewpoint of reducing capital investment and effective use of existing equipment. The system is very good.

  In this embodiment, sulfite black liquor and sulfite pulp obtained by sulfite cooking are separated by a separation device, the separated sulfite black liquor is sent to an ethanol fermentation device, and sulfite pulp is used as pulp Is done. The sulfite pulp obtained by separation is washed and bleached, and can be used as a cellulose fiber for papermaking and dissolving pulp, and can also be used as a fiber raw material such as rayon and lyocell.

  The sulfite black liquor sent to the ethanol fermentation apparatus is subjected to ethanol fermentation of the sugar content in the sulfite black liquor in the ethanol fermentation apparatus to obtain crude ethanol. Crude ethanol may be purified by a purification apparatus.

  The main component of the fermented liquid in which sugar is consumed in ethanol fermentation is lignin sulfonic acid. However, lignin sulfonic acid can be extracted from the fermented liquid and used, and lignin sulfonic acid can be used from the fermented liquid. It can also be used as thermal energy by a recovery boiler without being taken out. When taking out lignin sulfonic acid out of the system, the amount of heat energy recovered in this system is reduced, but for example, biomass energy recovered by combustion of kraft black liquor can be used. The usage mode of the fermented liquid may be appropriately changed in consideration of the operation state of the system and the effect / added value to be generated, and the ratio can be determined within a range that does not disturb the good balance of the system.

  In this embodiment, the fermented liquid is sent to a concentrator and concentrated to a solid concentration of about 50 to 70% by weight. The concentrated fermented liquor is sent to a recovery boiler, and injected in the recovery boiler to recover thermal energy. The recovered thermal energy may be used in any step of the present invention. For example, by using the recovered thermal energy in a distillation / purification process that requires the most energy in the bioethanol production process, It is possible to reduce the ethanol production cost. In addition, sodium and sulfur contained in the fermented liquor are collected and reused as kraft cooking chemicals.

  Moreover, in this aspect, a lignocellulose raw material is processed with a kraft cooking apparatus, and a kraft pulp and a kraft black liquor are obtained. Kraft pulp and kraft black liquor are separated by a separating device, and kraft pulp is used as a raw material for papermaking as pulp, and kraft black liquor is concentrated by a concentrator and then burned by a recovery boiler to recover thermal energy. At the same time, the cooking chemical is recovered as a white liquor. The white liquor can be treated with a causticizing device or the like to obtain calcium carbonate and sodium hydroxide.

  Conventionally, in the recovery and reuse of cooking chemicals in kraft cooking, fluctuations in the recovery rate balance of sodium and sulfur have been a major issue, but according to the present invention, the KP equipment and the SP equipment are provided together. Because it is possible to recover the fermented liquor derived from sulfite cooking and kraft black liquor in any ratio, it is easy to keep the balance of the KP production system optimal, and even in the kraft cooking process Give great benefits. A part of the smelt obtained from the recovery boiler can be taken out and recovered and reused as a cooking chemical for sulfite cooking.

  Moreover, this aspect is characterized in that sodium-based sulfite cooking equipment and bioethanol production equipment are provided side by side in equipment for producing pulp by the kraft method. In reality, kraft digesters (such as digesters), concentrators, recovery boilers, causticizers, etc. are built into kraft pulp manufacturing equipment. In this embodiment, for example, sulfite is used in KP manufacturing plants. It is possible to implement the present invention only by newly installing a cooking apparatus and an ethanol fermentation apparatus, which is extremely advantageous in terms of capital investment.

  FIG. 2 is a schematic view showing another embodiment of the present invention. In this embodiment, part or all of the pulp obtained by sulfite cooking is converted into a fermentable sugar solution by enzymatic decomposition, and ethanol fermentation using the obtained saccharified solution alone or in combination with black liquor. It is characterized by making it.

  For sulfite pulp obtained from lignocellulose raw material by sulfite digestion, when added value can be expected, it is preferable to commercialize itself as wood-based pulp / fiber and use it for ethanol fermentation. After the treatment, it can be used for ethanol fermentation. For example, when manufacturing sulfite pulp using conventional high-quality wood chips or raw materials of equivalent quality, it can be said that sulfite pulp itself is high in quality and has high added value, so it is preferable to use it as pulp. . On the other hand, sulfite pulp produced using chips prepared from forest land remnants, bamboo, thinned wood, construction waste, etc., as a lignocellulose raw material often has insufficient fiber strength and has added value as a pulp. Since it is relatively low, saccharification and ethanol fermentation are preferred because they can increase the added value of the product.

  In this embodiment, sulfite pulp is saccharified and subjected to ethanol fermentation. First, sulfite pulp is dispersed in water to form a slurry, the pH and temperature of the pulp slurry are adjusted within a range in which the enzyme exhibits activity, and cellulose is decomposed into glucose by an enzyme (cellulase) to prepare a saccharified solution. In the present invention, for example, the pH of the pulp slurry can be adjusted to 3 to 10, and the temperature can be adjusted to 5 to 80 ° C. Nutrient sources such as ammonia, ammonia phosphate, and urea are added to this saccharified solution, and ethanol is produced by ethanol fermentation using the action of microorganisms such as yeast. After ethanol fermentation, ethanol and fermented liquid are separated by rough distillation. The separated ethanol is again distilled and purified in the rectification column to become bioethanol. The cellulose saccharified solution obtained in this step may be used for ethanol fermentation alone, or may be mixed with sulfite black liquor for ethanol fermentation. Whether or not saccharified solution and sulfite black liquor are used in combination. May be appropriately selected according to the blending ratio of the two and the capacity / balance of the entire facility. Moreover, the fermentation apparatus which carries out ethanol fermentation of the saccharified liquid obtained from the sulfite pulp, and the fermentation apparatus which carries out ethanol fermentation of the sulfite black liquor may be different, or may be the same.

  The present inventor has found that sulfite pulp has a greater merit for saccharification and ethanol fermentation than kraft pulp. Advantages of using sulfite pulp for ethanol fermentation include a high enzymatic degradation rate and a need for less washing (deligening).

  Below, it demonstrates that it is advantageous to use sulfite pulp for ethanol fermentation compared with kraft pulp. In general, lignin is said to reduce the rate of degradation by the enzyme because it (i) adsorbs to the enzyme and inhibits the activity of the enzyme, and (ii) physically interferes with the attack of the enzyme on cellulose. It has been broken. For this reason, it was considered difficult to enzymatically treat the obtained pulp in an unbleached state, and it was thought that it was necessary to remove the lignin contained once. In particular, KP lignin is a thiolignin and generally has higher enzyme inhibition than lignin sulfonic acid. Therefore, when kraft pulp is enzymatically decomposed, kraft black liquor must be drained and then thoroughly washed to remove lignin. Further, in the kraft method, in order to increase the pulp yield, it is common not to carry out excessive treatment, and there is a tendency that a relatively large amount of lignin remains in the pulp fiber. For this reason, in order to use kraft pulp as a raw material for ethanol fermentation, it was necessary to carry out a bleaching treatment or the like. Thus, since kraft pulp can increase the activity of the cellulolytic enzyme to some extent and produce a saccharified solution by being accompanied by a bleaching step, if it is attempted to obtain a saccharified solution from kraft pulp, the production cost becomes high. .

  Although there are rarely present cellulolytic enzymes exhibiting activity in the alkaline region, most enzymes exhibit high activity in the acidic region. In addition, if the kraft pulp is not sufficiently washed and the pulp slurry contains a relatively large amount of lignin, the lignin is polycondensed and insolubilized as the pH value decreases (especially in the acidic region) due to pH adjustment, and the pulp fiber surface Adsorbed on the enzyme, the enzyme activity is inhibited. Furthermore, since kraft pulp contains a large amount of hemicellulose, it is necessary to use not only a cellulose-degrading enzyme but also a hemicellulose-degrading enzyme. However, since the optimum pH and temperature differ depending on each enzyme, it may be difficult to set optimum conditions depending on the combination of enzymes. Furthermore, since kraft pulp has little damage to pulp fibers, the amount of enzyme required for saccharification is large and the profitability is poor.

  On the other hand, when sulfite pulp obtained by sulfite digestion is treated with an enzyme, the lignin is not washed or removed so strongly (for example, even if it is separated from black liquor), it is efficient. It is possible to perform enzymatic treatment. The cause is not limited to this, but a difference in behavior of KP lignin and SP lignin (lignin sulfonic acid) in an acidic solution can be considered. That is, KP lignin is water-soluble in the alkaline region and relatively easy to remove, but when the pulp dispersion is acidified for enzyme treatment, lignin is polycondensed and insolubilized as described above. As a result, in the kraft pulp, when the lignin is not sufficiently washed and removed, the lignin deposits on the surface of the kraft pulp and inhibits the enzyme activity. On the other hand, since lignin sulfonic acid is sulfonated in the cooking process, it is stable even in an acidic region where cellulase having a high decomposition activity is high. Further, since the enzymatic treatment is carried out under acidic conditions, the hydrophilicity of SP lignin is lost, and SP lignin is stably dispersed in the pulp slurry without being deposited on the cellulose surface. As a result, SP lignin is unlikely to be a steric hindrance to the enzyme, and it is considered that the enzyme itself has little inhibitory property.

  In the sulfite method, by optimizing the cooking conditions, it is possible to moderately damage the cellulose fibers and loosen the bonds between the fibers, so that subsequent treatment with cellulolytic enzymes can be facilitated. It becomes. As a result, the amount of enzyme used and the processing time can be greatly reduced, and the cost required for saccharification of cellulose can be greatly reduced.

FIG. 1 is a schematic diagram showing an embodiment of the system of the present invention, in which only sulfite black liquor is used for ethanol fermentation. FIG. 2 is a schematic view showing an embodiment of the system of the present invention, in which sulfite black liquor and sulfite pulp are used for ethanol fermentation.

Claims (7)

A kraft cooking apparatus for kraft cooking the first lignocellulose raw material to obtain kraft pulp and kraft black liquor;
A sulfite cooking apparatus for sulfite cooking a second lignocellulose raw material on a sodium basis to obtain sulfite pulp and sulfite black liquor;
An ethanol fermentation apparatus for ethanol fermentation of sulfite black liquor to obtain ethanol and a fermented liquid;
A cooking chemical recovery device for recovering cooking chemicals contained in the kraft black liquor and the fermented liquid, and sending the recovered cooking chemicals to the kraft cooking device;
A system for producing ethanol using lignocellulose as a raw material.   The system of claim 1, wherein the cooking chemical recovery device comprises a recovery boiler.   The system according to claim 1 or 2, wherein the cooking chemical recovery device further comprises a causticizing device that causticizes the white liquor obtained from the recovery boiler to obtain calcium carbonate and sodium hydroxide.   The system according to any one of claims 1 to 3, wherein the lignocellulose raw material comprises wood chips prepared from coniferous and / or hardwoods.   The system according to any one of claims 1 to 4, wherein the lignocellulose raw material comprises bamboo, forest land residual material, and building waste material. Kraft cooking the first lignocellulose raw material to obtain kraft pulp and kraft black liquor;
Sulfite cooking the second lignocellulose raw material on a sodium basis to obtain sulfite pulp and sulfite black liquor;
Sulfite black liquor is ethanol fermented to obtain ethanol and fermented liquid;
Recovering cooking chemicals from the fermented liquor and kraft black liquor, and sending the recovered cooking chemicals to the kraft cooking process;
A process for producing ethanol using lignocellulose as a raw material.   The method according to claim 6, further comprising saccharifying the sulfite pulp obtained in the sulfite cooking step and subjecting the obtained saccharified solution to ethanol fermentation.

Images